Updates for RN 0.57.x compatibility

[dphaener]

This updates the config to be compatible with RN 0.57.x. The metro blacklist is in a different place, and it is now required that you specify the project root. This has been tested for backwards compatiblity with React Native down to 0.55.x.

[JustinKasad]

This PR works great!

Can we get this merged @jevakallio @jpdriver

[jpdriver]

hey @JustinKasad -- unfortunately Formidable Labs only has a finite amount of resources to spend on OSS projects; and since whackage was never as popular as some of our other projects we consider it officially archived (see note on README here)

please feel free to fork the repo and implement this change!

[dphaener]

@JustinKasad My company has a forked version of this that we have been updating. Currently it's a private repo, but I'll talk to my team about open sourcing it.