Base handler

This looks simple now, but the idea behind the song handler is that it
can work on mp4, wav, mp3 or whatever else. For now it just handles mp3
stuff.
Mutagen

Necessary. so cute. upgrade get. dependency so strong.
It compiles now

Sam, try it now. This is now ready to add as an import, though still
needs some more functionality. (woot)
Added a clean return class.

Now we can send in an expected list of values.
Merge pull request #3 from hackernight/Metadata-testing

Metadata testing