Adding note on Knuff-Framework

README.markdown

@@ -9,7 +9,7 @@ The debug application for Apple Push Notification Service (APNs).
 * Send push notifications to APNS (Apple Push Notification Service) very easily (no configuration needed at all)
 * Load / Save documents including token and JSON payload
 * Grabs the certificate right from your keychain
-* Get the device token automatically; forget about manually retrieving the device token through logging or similar techniques. Even more useful when not in sandbox mode
+* Get the device token automatically; forget about manually retrieving the device token through logging or similar techniques. Even more useful when not in sandbox mode (requires [Knuff-Framework](https://github.com/KnuffApp/Knuff-Framework))
 * Support for error response codes
 * Detects Development/Production environment automatically
 * Supports universal certificates