iOS 10 adds the UNUserNotificationCenterDelegate
protocol for handling notifications while your app is in the foreground.
- (void) userNotificationCenter:(UNUserNotificationCenter *) center
willPresentNotification:(UNNotification *) notification
withCompletionHandler:(void (^)(UNNotificationPresentationOptions options)) completionHandler
{
NSLog(@"Present notification from foreground");
completionHandler(UNNotificationPresentationOptionAlert + UNNotificationPresentationOptionSound);
}