Replacing WebSockets with Comet

- infinite iframe technique with long-lasting connection
- alerting users when the connection dies
- subscribers are removed if they don't ping the server in a given time-frame
- some browsers will display a forever loading wheel on the page, but this is the only technology that will work across all browsers & connections
Merge pull request #941 from delving/13.06-ws-to-comet

Replacing WebSockets with Comet