fix checking size from total message to payload (part of message)
fix checking size from total message to payload (part of message)

see https://developer.apple.com/library/mac/#documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/ApplePushService/ApplePushService.html#//apple_ref/doc/uid/TP40008194-CH100-SW1
"The maximum size allowed for a notification payload is 256 bytes"

mbartmann/apn_on_rails,STRd6/apn_on_rails,digisight/apn_on_rails