Include player context with player state (like the iOS SDK)

[djwillcaine]

With the iOS version of this SDK, the player context (current album/playlist) is included along with the player state. However, in this android implementation, it is not, and instead we have to separately subscribe to the player context.

It would be really nice to see some better consistency accross the iOS and Android SDKs. This is not the only difference, but is the one that is most frustrating for me personally. I don't really see any need for a separate event listener for the context when a change in context means there must also be a change in player state. It makes much more sense to bundle these together, as on the iOS version.