STOMP 1.1 Over WebSocket

* update stomp.js library to support STOMP 1.1 (including
  heart-beating).
* The js file was taken from  https://raw.github.com/jmesnil/stomp-websocket/master/dist/stomp.js.

I did not find the source of the [Web-Stomp plugin](http://www.rabbitmq.com/web-stomp.html) but its "Missing Features" section can be removed now that STOMP 1.1 [heart-beating is supported](http://www.jmesnil.net/stomp-websocket/doc/#heartbeat).