Basic queue functionality

The commit below adds basic queue functionality which is pretty basic, but has necessary code. The queue currently handles validating the songs coming down from firebase, as well as sending error reporting up to firebase. It also handles (obviously) holding a FIFO structure for songs that will be handed to the Spotify player code that will be in the next pr (hopefully). 

![photo on 7-21-13 at 1 05 am](https://f.cloud.github.com/assets/2166815/831403/4e3a5f92-f1dc-11e2-8ee5-59f374ffd2b4.jpg)