Use Google Music from inside Jukebox

What
---
Using gmusicapi Jukebox now supports the use of GoogleMusic accounts.

Adding a new GooglePlayStorage('username', 'password') 

What is still to do:
Add MultipleStorage to access multiple users accounts as well as local accounts.
Have a smarter Authentication layer when the session expires.
I am not sure why this is subclassing`MemoryStorage` I don't think `add_song` or `del_song` are correct.