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
Also, is there any way to move this sub class outside of the Winamp class? I'm all for abstracting similar functionality into a class, but the main advantage I see is that it shrinks each class making them easier to read.