Update gemfile

Remove some crud, add a known good version of jquery-rails for ember
Switch to newer version of ember
Simple demo

Can't drag and drop anything yet, but it displays some dummy content.

TODO:
* make it so the "Extra Commas" container lets you drag and drop commas
  to and from it
* make it so sentences are a drop target that changes the actual sentence
* make it so you can drag the commas OFF the sentences
  (this will probably require making the sentences object aware of its commas)
Cleanup the demo a little bit
Add an object for individual words

These will be the drop targets, not the actual sentence. A sentence view will
contain multiple words that are drop targets.

Probably should see if there is a better way of splitting on __any__ whitespace.
Split drag and drop into a separate file
Words are now drop targets
Words accept commas

Hooray bindings!
Add README
Add a small hint to explain how this works

It's not very obvious that this supports drag and drop, so I wanted to
explain how you might use this interface.
Fixup javascript for heroku

I haven't pushed a new rails app to heroku in a while, so I wasn't familiar with the
asset pipeline changes.