I'd like to experiment with `await`ing Rx observab...

# coroutines

[kirillrakhman]

I'd like to experiment with `await`ing Rx observables or posting to an Android Handler or maybe ViewTreeObserver. The fact that `async`/`await` is a library feature and not bound to a specific Task class like in C#, means we will probably need separate implementations for all kinds of `await`able stuff, right?