Added subscribe and unsubscribe channel events

Are you open to adding in subscribe and unsubscribe events?

I also set max listeners on the channel to infinite to work around the warning about exceeding 10 listeners per [emitter.setMaxListeners()](http://nodejs.org/docs/v0.11.12/api/events.html#events_emitter_setmaxlisteners_n). Not sure if you want that either.

Just thought I'd throw this out there.

Cheers and thanks! :beers: