Update .travis.yml for Swift Package Manager support
Update .travis.yml for Swift Package Manager support

calebd/ReactiveCocoa,calebd/ReactiveCocoa,sandyway/ReactiveCocoa,sandyway/ReactiveCocoa,ReactiveCocoa/ReactiveSwift,ikesyo/ReactiveCocoa,walkingsmarts/ReactiveCocoa,walkingsmarts/ReactiveCocoa,sandyway/ReactiveCocoa,calebd/ReactiveCocoa,victorlin/ReactiveCocoa,ReactiveCocoa/ReactiveSwift,victorlin/ReactiveCocoa,victorlin/ReactiveCocoa,walkingsmarts/ReactiveCocoa,ohwutup/ReactiveCocoa,ikesyo/ReactiveCocoa,ohwutup/ReactiveCocoa,ReactiveCocoa/ReactiveSwift,ohwutup/ReactiveCocoa