Update for Xcode 6.1

- Utilize `rawValue` instead of `toRaw()` due to method being removed.
- Fixes various compiler warnings surfacing in Xcode 6.1.

More information in the Xcode 6.1 [release notes])(https://developer.apple.com/library/ios/releasenotes/DeveloperTools/RN-Xcode/Chapters/xc6_release_notes.html#//apple_ref/doc/uid/TP40001051-CH4-DontLinkElementID_23).