Adopt native coroutines

[kevin-bates]

Once Python 2 support has been removed (#63), we should update the coroutine decorators and associated backward compatible constructs to use native coroutines (async def and await).

[SylvainCorlay]

There was a massive PR by @blink1073 #23 which did exactly that. At the time, it was decided to not go with this right away to remain closer to the notebook codebase for a little bit longer.

Maybe we want to go ahead with this now.

[kevin-bates]

@SylvainCorlay - I'm sorry I didn't catch that - thanks (and thanks @blink1073!)

I think once we've brought over the remaining notebook commits, we should embark on such a thing. (I suppose we should hold off on #90 until then as well.) Do we have an enumeration of which commits we should cherry-pick?

[Zsailer]

Funny enough, I'm working on the notebook PR porting now...

[Zsailer]

These were all updated in #191! 🎉 Closing!