Support async/await

[lacker]

We'll want to support it eventually, the only question is when.

In #43 @gaearon stated

Not adding async yet because I’ll need to understand its stability better before doing it.

so that's the status quo.

[gaearon]

We’ll also need to choose our stance on polyfills. Do we leave it to user to polyfill Promise?

[insin]

Will anyone be likely to be using async without fetch() (and a polyfill for it)? The most popular polyfill for it requires you to bring your own Promise polyfill, as does axios.

Will the runtime transform be used to inject the regenerator runtime only when needed? It also does local polyfilling, but you can configure that off.

[gaearon]

To be honest I’m not familiar with all these tradeoffs so it’s hard for me to say. 😄
What do you think would be good defaults?
I want to make it easy to get started with common code samples but also to avoid crazy bundle size.

[insin]

This might be a decent default for async/await support in addition to the plugin for transforming the syntax into generators - it will pull in the regenerator runtime only if async/await is used (and will also import babel-runtime helpers instead of duplicating them in each module they're needed in) while leaving polyfilling entirely in the hands of users.

["babel-plugin-transform-runtime", {
  "polyfill": false,
  "regenerator": true
}]

[gaearon]

Would you like to make a PR adding a sensible async support setup?

[kennetpostigo]

I think #327 adds support for this. Is it okay to close this?

[gaearon]

Yep, thanks!