Renamed the oauth property inside the JPImgurClient class
Modified the authenticateUsingOAuthWithPIN:success:failure method to handle the authorization header
Added proper parameters to obtain JSON responses
Updated JPImgurKit.h to include models
Overrided setAuthorizationHeaderWithToken method to support Bearer type by default
Added declaration of the overridden method initWithBaseURL

All the uncommon methods I override will now be declared for better
documentation
Added an access token property to the .plist file used for tests