make example runnable

README.md

@@ -31,13 +31,16 @@ var pack = tar.pack() // pack is a streams2 stream
 pack.entry({ name: 'my-test.txt' }, 'Hello World!')
 
 // add a file called my-stream-test.txt from a stream
-var entry = pack.entry({ name: 'my-stream-test.txt' }, function(err) {
+var entry = pack.entry({ name: 'my-stream-test.txt', size: 11 }, function(err) {
   // the stream was added
   // no more entries
   pack.finalize()
 })
 
-someEntryStream.pipe(entry)
+entry.write('hello')
+entry.write(' ')
+entry.write('world')
+entry.end()
 
 // pipe the pack stream somewhere
 pack.pipe(process.stdout)