Updates changelog with 2.0.0-rc.0 changes.
Updates changelog with 2.0.0-rc.0 changes.

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