Fixes bug in which user would not be removed from channel upon disconnecting

* updateChannelStatus now correctly responds to disconnect and calls new function freeUpChannel
* freeUpChannel removes user from channel for two situations - when a user is leaving a song for another song and when a user is disconnecting
* removing gumby.retina.js as no longer using it
removing commented unused code
Merge pull request #47 from artfoundry/bugs

Bugs