Update xcode and carthage in travis
Update xcode and carthage in travis

ohwutup/ReactiveCocoa,calebd/ReactiveCocoa,walkingsmarts/ReactiveCocoa,ohwutup/ReactiveCocoa,ohwutup/ReactiveCocoa,RACCommunity/Rex,walkingsmarts/ReactiveCocoa,ikesyo/Rex,RACCommunity/Rex,calebd/ReactiveCocoa,bjarkehs/Rex,RACCommunity/Rex,neilpa/Rex,calebd/ReactiveCocoa,neilpa/Rex,ikesyo/Rex,walkingsmarts/ReactiveCocoa,bjarkehs/Rex