Fixed issue where I wasn't updating the state to SUBSCRIBE_SENT when subscribing to channels that had been queued until the connected callback is received. Also fixed clear() method so that it clears out the queued subscriptions. Had to make InternalChannel implement Comparable because I'm now storing them in a ConcurrentSkipListMap inside ChannelManager (to avoid ConcurrentModificationExceptions when subscribing and removing within a loop) and the ConcurrentSkipListMap is a sorted map, so the keys must be comparable.