Adds support for 'content-available' key from commit 9a1a1b3 in ZendService_Apple_Apn
Adds support for 'content-available' key from commit 9a1a1b3 in ZendService_Apple_Apn

grigoritaadrian/NotificationPusher,monove/NotificationPusher,unit27/NotificationPusher,Doka-NT/NotificationPusher,boboldehampsink/NotificationPusher,angelitodelcielo/NotificationPusher,Ph3nol/NotificationPusher,SoldierCorp/NotificationPusherNoBadge,lode/NotificationPusher