Tightening up some state handling. Also works around a bug where going to the background and returning would cause the player state to get out of synch due to the avqueueplayer's rate dropping to zero but not sending KVO when it changes back to 1.
Updating json format for play response ("blip" dict was flattened)
Adding FMReachability implementation, which requires SystemConfiguration.framework. If never used, consider removing in order to save the extra dependency.