Implement Plex with (web)sockets

*:warning: Not ready for merge* 

Instead of constantly polling the client we can try something like web sockets where we only create a connection once and listen to changes. I haven't verified that Plex supports this, but it is documented in XBMC's [JSON-RPC](http://wiki.xbmc.org/index.php?title=JSON_RPC#WebSocket) documentation.

We know that Plex Home Theatre is based off of XBMC "Frodo" which implements the [v6 API](http://wiki.xbmc.org/index.php?title=JSON-RPC_API/v6).