bump ios.platform to 6.0
bump ios.platform to 6.0

required to use dispatch_queue_t as regular Objective-C (for ARC
support)

iosphere/MQTTKit,JackLeeMing/MQTTKit,mobile-web-messaging/MQTTKit,jmesnil/MQTTKit,jmesnil/MQTTKit,cnbin/MQTTKit,iosphere/MQTTKit,cnbin/MQTTKit,nodeath/MQTTKit,mobile-web-messaging/MQTTKit,NormanLeeIOS/MQTTKit,mwoytowich/MQTTKit,JackLeeMing/MQTTKit,Movile/MQTTKit,nodeath/MQTTKit,nodeath/MQTTKit,JackLeeMing/MQTTKit,NormanLeeIOS/MQTTKit,mobile-web-messaging/MQTTKit,cnbin/MQTTKit,mwoytowich/MQTTKit