fast-async babel plugin modifies `Function.prototype` globally

[fmnxl]

I wonder if we can let the user decide to use fast-async themselves, rather than being baked in this project.

One reason could be that it can impact other parts of their app (see my PR to react-native facebook/react-native#27264).

It currently breaks react native apps that does dynamic styling through passing a function to StyleSheet.create

[tannerlinsley]

I would be okay moving back to the generator transformer. As long as someone PRs something to the docs on how to properly use fast-async

[tannerlinsley]

Would you be willing to do that?

[fmnxl]

Yes! I'll submit a PR :)

[fmnxl]

I think I've found another solution: exclude nodent runtime.

#52.