Use async–await in twinkle?

[siddharthvp]

While async-await is I think currently usable in twinkle clients, it is not currently being used in twinkle-core at all. The reason is mainly that the webpack/babel transpile async-await to generators, which are awkward and can be hard to debug.

However, async-await can simplify things quite a bit and make code more readable in many places.