Integrate prettier for `--fix`

[brandonocasey]

This should allow us to have much more control over the resulting code from --fix

See: https://github.com/prettier/prettier

[gkatsev]

I don't think we should do this. We should either use prettier and integrate it as a precommit hook or something or just continue using eslint.
I'm leaning towards just staying with eslint for now, especially since --fix works with quite a lot of stuff now.