Make ARC compatible
Remove NSData+Base64.

iOS 7 and OS X 10.9 now include NSData base64EncodedStringWithOptions:
so this is no longer necessary if those are the minimum requirements.
Move ParseURLQueryString to OAuthCore instead of NSURL category
Move ActualPath to OAuthCore instead of NSURL category
Move Nonce to OAuthCore instead of NSString category
Move RFC3986EncodedString to OAuthCore instead of NSString category
Suggest to the compiler to inline functions
Shorten parameter names
Convert to modern Objective-C syntax
Personal taste formatting changes