RxKotlin 2.0 RC1

This is the release candidate for RxKotlin 2.0, which is backed by RxJava 2.x.

The API highly mirrors the release candidate of RxKotlin 1.0, but of course accommodates the types and nuances of RxJava 2.0.

Here is a list of differences from the RxKotlin 1.0 version:

• Package domain is io.reactivex.rxkotlin
• Extensions are applicable to Observable and Flowable
• Extension functions targeting null emissions have been removed
• Extension functions have been added for Single, Maybe, and Completable
• onComplete is the completion event name instead of onCompleted
• Extension functions targeting Subscription now target Disposable