2.0.0-RC3 preparations

[akarnokd]

Version 2.0.0-RC3 - September 23, 2016 (Maven)

This Release Candidate features mostly internal cleanups of code and Javadoc, Reactive-Streams Test Compatibility Kit implementations (and thus verification) of our Flowable implementation and additional unit-test coverage. Big tanks to @vanniktech for the many contributions and @JakeWharton for the continued reviews.

Other notable changes:

• The new Maybe type of RC2 now features all relevant operators.
• Many Observable and Flowable operators now return Single or Maybe.
• Pull 4525 : Fixed generics of combineLatest and zip because Function<? super T[], R> doesn't work.
• Pull 4522 : Fixed delay operator to call onError on the provided scheduler
• Pull 4490 : rename isCancelled to isDisposed inside the varios emitters of create()
• Pull 4504 : add default XObserver implementation to Single, Maybe and Completable
• Pull 4518 : add ResourceXObserver implementation to Single, Maybe and Completable
• Pull 4536 : fix timeout operators not properly cancelling/disposing the upstream.
• Pull 4583 : Flowable.create()'s FlowableEmitter didn't handle nulls properly.
• Pull 4586 : Add error assertion with predicate to TestSubscriber and TestObserver.

In addition, the wiki page What's different in 2.0 has been extended with more information.

[akarnokd]

Closing via https://github.com/ReactiveX/RxJava/releases/tag/v2.0.0-RC3