Change how we integrate spotify with Android

Hey @cjam I was doing some tests and I believe that we should move how we do the android integration. We should move the dependency to be direct from auth library that Spotify now releases using maven. The other point is that other Spotify libs like the Flutter one you need to direct add the `aar` yourself, and I think we should do the same path.

I will send a PR with those ideas and we can discuss on top of it.