Adding reddit OAuth2 classes

Hey Fernandez,

So I decided I wanted to make a Reddit bot and started making a Reddit OAuth2 implementation for Scribe. Only after getting most of the work done (its really not much) did I realize that a bot does not use OAuth by definition - since a bot will have it's own user account, I can just login the 'normal' way and not use OAuth authentication.

Rather than throw away this work, I'd like to submit this pull request. If anything is not up to par please let me know.