Added support for Parse and re-organized project structure for easier management.

I've been working to add support for Parse, and I also changed the project structure a bit so that Providers are in their own folders. Considering how many potential providers this kit could eventually have, I think this organization makes more sense.

One thing to note is that Parse support comes via a new pod I created called Parse-iOS-SDK. At the time of submitting this pull request, it has yet to be merged into the master Cocoapods repo.