Added support to play/pause playback on screensaver start/stop.

This should close #135. Pictured below is the only UI change.
![screen shot 2013-08-07 at 0 19 36](https://f.cloud.github.com/assets/3893828/922282/fcc33844-ff20-11e2-8a8a-4a447bfac418.png)