Notification format 2

Apple “deprecated” simple and enhanced notification formats, and provides a new format “2” which seems more flexible for the future (see https://developer.apple.com/library/ios/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/Chapters/CommunicatingWIthAPS.html).

The pull request also includes specs for the Notification type and some minor changes to be able to use Simplecov in the project (I found that Venice was using those two gems, so I decided to go with them).

Also included a little fix for a strange status sent by Apple, which wasn’t handled correctly.