Refactor/es modules

[Andarist]

This fixes #302

@benjamn
So Im mostly done when it comes to refactoring regenerator-runtime.

The missing piece is to change regenerator-transform so it adds an import statement to the regenerator-runtime module. Im not strong with AST (although I know the basics) so an advice how this should be handled would be greatly appreciated! :)

Whats the best way to add a single import statement for a file with multiple generators?
How we differentiate what type of import (es/cjs) should be added?
Do we need to support a use case of including the regenerator itself in the outputted bundle? When?

[benjamn]

Could we copy the logic of babel-plugin-transform-runtime? Hopefully that should work even if transform-runtime is not otherwise being used.

[Andarist]

@benjamn ive finished working on this, please take a look - aint sure if regenerator-transform adjustments were made in the best possible way, but its working 🎉

Please review and let me know if there is anything I need to do to advance it further :)

Once this gets merged (and published) I'll try to update most notable projects depending on those packages.

[Andarist]

@benjamn rebased against recent master

[Andarist]

@benjamn any chances this could get reviewed? 😃

Unfortunately at the moment Im not sure why travis is failing, because locally everything is working fine. It would be great to debug it in ssh mode, but I dont have needed permissions to do it myself.

[Andarist]

Hey @benjamn . I know you are extremely busy, I'm just pinging friendly here about this PR :)

[brettz9]

Could this be (rebased and) reviewed? With @babel/polyfill deprecated, there is no (direct) ESM replacement.

[agilgur5]

@benjamn is there any chance you or someone from FB would be able to resurrect this? Don't mean to necro or force any work, but was hoping there might be a way to prioritize this especially as this is still under FB's org (and therefore theoretically supported by a very large company).
A lot of issues in the community end up pointing here to this PR that was never reviewed, so it doesn't seem as if there's much the community can do right now (other than fork) 😕

In particular, as #302 (comment) / babel/babel-polyfills#59 point out, this PR would enable a "pure" polyfill. Currently all usage of regenerator-runtime causes pollution of global scope, which is not ideal for library authors.