Use modern notification format.

New development should use the modern format to connect to APNs, as described in [The Binary Interface and Notification Format.](https://developer.apple.com/library/ios/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/Chapters/CommunicatingWIthAPS.html#//apple_ref/doc/uid/TP40008194-CH101-SW4)