Adds `swift-3.0` as valid branch in Dangerfile.
Adds `swift-3.0` as valid branch in Dangerfile.

shiratsu/RxSwift,ReactiveX/RxSwift,KyoheiG3/RxSwift,ReactiveX/RxSwift,kzaher/RxSwift,shiratsu/RxSwift,tottakai/RxSwift,tottakai/RxSwift,tottakai/RxSwift,KyoheiG3/RxSwift,KyoheiG3/RxSwift,cfraz89/RxSwift,kzaher/RxSwift,cfraz89/RxSwift,shiratsu/RxSwift,ReactiveX/RxSwift,cfraz89/RxSwift,kzaher/RxSwift,kzaher/RxSwift,cfraz89/RxSwift