Added support for iOS 7

As outlined in:

https://developer.apple.com/library/ios/documentation/uikit/reference/UIApplicationDelegate_Protocol/Reference/Reference.html#//apple_ref/occ/intfm/UIApplicationDelegate/application:didReceiveRemoteNotification:

    If your delegate also implements the application:didReceiveRemoteNotification:fetchCompletionHandler: method, the app object calls that method instead of this one.