Fix typo
Return true/false for success/fail on iOS

This is what is expected to be returned by 
RMS\PushNotificationsBundle\Service\Notifications
and
RMS\PushNotificationsBundle\Service\OS\OSNotificationServiceInterface
and is what happens with Android and Blackberry

Also keep track of errors a bit. Needs more work to expose them nicely.
Merge pull request #36 from whiteoctober/master

Fix return value in iOS