Issue #29 Pressing play while playing should restart the current track

- If already playing, use existing stop.
- Included underscore.js in project to make searching arrays easier. Can refactor to vanilla JS w/o library

Cheers
Okay. I kinda got that. However, it seemed odd to me to go to such great lengths to add a layer around the `Media` object actions and then access the media object directly for the event listeners later on. Any thoughts on that?