Add travis config.
Add travis config.

ashfurrow/ReactiveViewModel,fxd/ReactiveViewModel,nickcheng/ReactiveViewModel,jackgao2016/ReactiveViewModel,iguchunhui/ReactiveViewModel,TeehanLax/ReactiveViewModel,jackgao2016/ReactiveViewModel,SummerHanada/ReactiveViewModel,ashfurrow/ReactiveViewModel,ReactiveCocoa/ReactiveViewModel,takeshineshiro/ReactiveViewModel,takeshineshiro/ReactiveViewModel,iguchunhui/ReactiveViewModel,nickcheng/ReactiveViewModel,SummerHanada/ReactiveViewModel,ReactiveCocoa/ReactiveViewModel,nickcheng/ReactiveViewModel,fxd/ReactiveViewModel