Revert recent Gemfile changes.

* 187fb9405db5c44f1323590293eb7fc7aee8e127.
* 2ffb33f58d5b87050a2d059545e5c8b9e5e6c151.
* f8ff7dc6cd590a596c2d150fa91bbd5d0116e32f.

It's causing `wrong constant name` and various other errors for me.