diff --git a/app/assets/javascripts/app/lib/base/jquery.caret.js b/app/assets/javascripts/app/lib/base/jquery.caret.js
new file mode 100644
index 000000000..651e037c6
--- /dev/null
+++ b/app/assets/javascripts/app/lib/base/jquery.caret.js
@@ -0,0 +1,367 @@
+//@ sourceMappingURL=jquery.caret.map
+/*
+  Implement Github like autocomplete mentions
+  http://ichord.github.com/At.js
+
+  Copyright (c) 2013 chord.luo@gmail.com
+  Licensed under the MIT license.
+*/
+
+
+/*
+本插件操作 textarea 或者 input 内的插入符
+只实现了获得插入符在文本框中的位置，我设置
+插入符的位置.
+*/
+
+
+(function() {
+  (function(factory) {
+    if (typeof define === 'function' && define.amd) {
+      return define(['jquery'], factory);
+    } else {
+      return factory(window.jQuery);
+    }
+  })(function($) {
+    "use strict";
+    var EditableCaret, InputCaret, Mirror, Utils, discoveryIframeOf, methods, oDocument, oFrame, oWindow, pluginName, setContextBy;
+    pluginName = 'caret';
+    EditableCaret = (function() {
+      function EditableCaret($inputor) {
+        this.$inputor = $inputor;
+        this.domInputor = this.$inputor[0];
+      }
+
+      EditableCaret.prototype.setPos = function(pos) {
+        return this.domInputor;
+      };
+
+      EditableCaret.prototype.getIEPosition = function() {
+        return this.getPosition();
+      };
+
+      EditableCaret.prototype.getPosition = function() {
+        var inputor_offset, offset;
+        offset = this.getOffset();
+        inputor_offset = this.$inputor.offset();
+        offset.left -= inputor_offset.left;
+        offset.top -= inputor_offset.top;
+        return offset;
+      };
+
+      EditableCaret.prototype.getOldIEPos = function() {
+        var preCaretTextRange, textRange;
+        textRange = oDocument.selection.createRange();
+        preCaretTextRange = oDocument.body.createTextRange();
+        preCaretTextRange.moveToElementText(this.domInputor);
+        preCaretTextRange.setEndPoint("EndToEnd", textRange);
+        return preCaretTextRange.text.length;
+      };
+
+      EditableCaret.prototype.getPos = function() {
+        var clonedRange, pos, range;
+        if (range = this.range()) {
+          clonedRange = range.cloneRange();
+          clonedRange.selectNodeContents(this.domInputor);
+          clonedRange.setEnd(range.endContainer, range.endOffset);
+          pos = clonedRange.toString().length;
+          clonedRange.detach();
+          return pos;
+        } else if (oDocument.selection) {
+          return this.getOldIEPos();
+        }
+      };
+
+      EditableCaret.prototype.getOldIEOffset = function() {
+        var range, rect;
+        range = oDocument.selection.createRange().duplicate();
+        range.moveStart("character", -1);
+        rect = range.getBoundingClientRect();
+        return {
+          height: rect.bottom - rect.top,
+          left: rect.left,
+          top: rect.top
+        };
+      };
+
+      EditableCaret.prototype.getOffset = function(pos) {
+        var clonedRange, offset, range, rect;
+        if (oWindow.getSelection && (range = this.range())) {
+          if (range.endOffset - 1 < 0) {
+            return null;
+          }
+          clonedRange = range.cloneRange();
+          clonedRange.setStart(range.endContainer, range.endOffset - 1);
+          clonedRange.setEnd(range.endContainer, range.endOffset);
+          rect = clonedRange.getBoundingClientRect();
+          offset = {
+            height: rect.height,
+            left: rect.left + rect.width,
+            top: rect.top
+          };
+          clonedRange.detach();
+        } else if (oDocument.selection) {
+          offset = this.getOldIEOffset();
+        }
+        if (offset) {
+          offset.top += $(oWindow).scrollTop();
+          offset.left += $(oWindow).scrollLeft();
+        }
+        return offset;
+      };
+
+      EditableCaret.prototype.range = function() {
+        var sel;
+        if (!oWindow.getSelection) {
+          return;
+        }
+        sel = oWindow.getSelection();
+        if (sel.rangeCount > 0) {
+          return sel.getRangeAt(0);
+        } else {
+          return null;
+        }
+      };
+
+      return EditableCaret;
+
+    })();
+    InputCaret = (function() {
+      function InputCaret($inputor) {
+        this.$inputor = $inputor;
+        this.domInputor = this.$inputor[0];
+      }
+
+      InputCaret.prototype.getIEPos = function() {
+        var endRange, inputor, len, normalizedValue, pos, range, textInputRange;
+        inputor = this.domInputor;
+        range = oDocument.selection.createRange();
+        pos = 0;
+        if (range && range.parentElement() === inputor) {
+          normalizedValue = inputor.value.replace(/\r\n/g, "\n");
+          len = normalizedValue.length;
+          textInputRange = inputor.createTextRange();
+          textInputRange.moveToBookmark(range.getBookmark());
+          endRange = inputor.createTextRange();
+          endRange.collapse(false);
+          if (textInputRange.compareEndPoints("StartToEnd", endRange) > -1) {
+            pos = len;
+          } else {
+            pos = -textInputRange.moveStart("character", -len);
+          }
+        }
+        return pos;
+      };
+
+      InputCaret.prototype.getPos = function() {
+        if (oDocument.selection) {
+          return this.getIEPos();
+        } else {
+          return this.domInputor.selectionStart;
+        }
+      };
+
+      InputCaret.prototype.setPos = function(pos) {
+        var inputor, range;
+        inputor = this.domInputor;
+        if (oDocument.selection) {
+          range = inputor.createTextRange();
+          range.move("character", pos);
+          range.select();
+        } else if (inputor.setSelectionRange) {
+          inputor.setSelectionRange(pos, pos);
+        }
+        return inputor;
+      };
+
+      InputCaret.prototype.getIEOffset = function(pos) {
+        var h, textRange, x, y;
+        textRange = this.domInputor.createTextRange();
+        pos || (pos = this.getPos());
+        textRange.move('character', pos);
+        x = textRange.boundingLeft;
+        y = textRange.boundingTop;
+        h = textRange.boundingHeight;
+        return {
+          left: x,
+          top: y,
+          height: h
+        };
+      };
+
+      InputCaret.prototype.getOffset = function(pos) {
+        var $inputor, offset, position;
+        $inputor = this.$inputor;
+        if (oDocument.selection) {
+          offset = this.getIEOffset(pos);
+          offset.top += $(oWindow).scrollTop() + $inputor.scrollTop();
+          offset.left += $(oWindow).scrollLeft() + $inputor.scrollLeft();
+          return offset;
+        } else {
+          offset = $inputor.offset();
+          position = this.getPosition(pos);
+          return offset = {
+            left: offset.left + position.left - $inputor.scrollLeft(),
+            top: offset.top + position.top - $inputor.scrollTop(),
+            height: position.height
+          };
+        }
+      };
+
+      InputCaret.prototype.getPosition = function(pos) {
+        var $inputor, at_rect, end_range, format, html, mirror, start_range;
+        $inputor = this.$inputor;
+        format = function(value) {
+          return $('<div></div>').text(value).html().replace(/\r\n|\r|\n/g, "<br/>").replace(/\s/g, "&nbsp;");
+        };
+        if (pos === void 0) {
+          pos = this.getPos();
+        }
+        start_range = $inputor.val().slice(0, pos);
+        end_range = $inputor.val().slice(pos);
+        html = "<span style='position: relative; display: inline;'>" + format(start_range) + "</span>";
+        html += "<span id='caret' style='position: relative; display: inline;'>|</span>";
+        html += "<span style='position: relative; display: inline;'>" + format(end_range) + "</span>";
+        mirror = new Mirror($inputor);
+        return at_rect = mirror.create(html).rect();
+      };
+
+      InputCaret.prototype.getIEPosition = function(pos) {
+        var h, inputorOffset, offset, x, y;
+        offset = this.getIEOffset(pos);
+        inputorOffset = this.$inputor.offset();
+        x = offset.left - inputorOffset.left;
+        y = offset.top - inputorOffset.top;
+        h = offset.height;
+        return {
+          left: x,
+          top: y,
+          height: h
+        };
+      };
+
+      return InputCaret;
+
+    })();
+    Mirror = (function() {
+      Mirror.prototype.css_attr = ["borderBottomWidth", "borderLeftWidth", "borderRightWidth", "borderTopStyle", "borderRightStyle", "borderBottomStyle", "borderLeftStyle", "borderTopWidth", "boxSizing", "fontFamily", "fontSize", "fontWeight", "height", "letterSpacing", "lineHeight", "marginBottom", "marginLeft", "marginRight", "marginTop", "outlineWidth", "overflow", "overflowX", "overflowY", "paddingBottom", "paddingLeft", "paddingRight", "paddingTop", "textAlign", "textOverflow", "textTransform", "whiteSpace", "wordBreak", "wordWrap"];
+
+      function Mirror($inputor) {
+        this.$inputor = $inputor;
+      }
+
+      Mirror.prototype.mirrorCss = function() {
+        var css,
+          _this = this;
+        css = {
+          position: 'absolute',
+          left: -9999,
+          top: 0,
+          zIndex: -20000
+        };
+        if (this.$inputor.prop('tagName') === 'TEXTAREA') {
+          this.css_attr.push('width');
+        }
+        $.each(this.css_attr, function(i, p) {
+          return css[p] = _this.$inputor.css(p);
+        });
+        return css;
+      };
+
+      Mirror.prototype.create = function(html) {
+        this.$mirror = $('<div></div>');
+        this.$mirror.css(this.mirrorCss());
+        this.$mirror.html(html);
+        this.$inputor.after(this.$mirror);
+        return this;
+      };
+
+      Mirror.prototype.rect = function() {
+        var $flag, pos, rect;
+        $flag = this.$mirror.find("#caret");
+        pos = $flag.position();
+        rect = {
+          left: pos.left,
+          top: pos.top,
+          height: $flag.height()
+        };
+        this.$mirror.remove();
+        return rect;
+      };
+
+      return Mirror;
+
+    })();
+    Utils = {
+      contentEditable: function($inputor) {
+        return !!($inputor[0].contentEditable && $inputor[0].contentEditable === 'true');
+      }
+    };
+    methods = {
+      pos: function(pos) {
+        if (pos || pos === 0) {
+          return this.setPos(pos);
+        } else {
+          return this.getPos();
+        }
+      },
+      position: function(pos) {
+        if (oDocument.selection) {
+          return this.getIEPosition(pos);
+        } else {
+          return this.getPosition(pos);
+        }
+      },
+      offset: function(pos) {
+        var offset;
+        offset = this.getOffset(pos);
+        return offset;
+      }
+    };
+    oDocument = null;
+    oWindow = null;
+    oFrame = null;
+    setContextBy = function(settings) {
+      var iframe;
+      if (iframe = settings != null ? settings.iframe : void 0) {
+        oFrame = iframe;
+        oWindow = iframe.contentWindow;
+        return oDocument = iframe.contentDocument || oWindow.document;
+      } else {
+        oFrame = void 0;
+        oWindow = window;
+        return oDocument = document;
+      }
+    };
+    discoveryIframeOf = function($dom) {
+      var error;
+      oDocument = $dom[0].ownerDocument;
+      oWindow = oDocument.defaultView || oDocument.parentWindow;
+      try {
+        return oFrame = oWindow.frameElement;
+      } catch (_error) {
+        error = _error;
+      }
+    };
+    $.fn.caret = function(method, value, settings) {
+      var caret;
+      if (methods[method]) {
+        if ($.isPlainObject(value)) {
+          setContextBy(value);
+          value = void 0;
+        } else {
+          setContextBy(settings);
+        }
+        caret = Utils.contentEditable(this) ? new EditableCaret(this) : new InputCaret(this);
+        return methods[method].apply(caret, [value]);
+      } else {
+        return $.error("Method " + method + " does not exist on jQuery.caret");
+      }
+    };
+    $.fn.caret.EditableCaret = EditableCaret;
+    $.fn.caret.InputCaret = InputCaret;
+    $.fn.caret.Utils = Utils;
+    return $.fn.caret.apis = methods;
+  });
+
+}).call(this);