Simplify embed/weblib code with Promise and async/await

[mihailik]

Those make code way simpler to track and follow, and can be transcoded back to ES5 safely.

[jeffpar]

True, any async code I wrote pre-dates async/await (and probably isn't very well written by today's standards), but as long as it's not broken, it's low on my mental list of priorities. Not to say I wouldn't happily accept rewrites of any old crappy code.