support for async/await

[orefalo]

callback are so 70s

[pelger]

LOL - Callbacks are at least 90's be fair!

[davidmarkclements]

should be noted that for something low level and and in a potential hot path, async/await is unsuitable for performance. Currently async/await will create a minumum of four promises for each invocation, this is as per spec. Promises are heavy as it is.

[pelger]

Fair point! That being said I'm not against providing an async/await use pattern here as an alternative to the callback interface. Looking forward to the PR :)