Update changes.md for RC3

Author: akarnokd

CHANGES.md

@@ -2,6 +2,25 @@
 
 Version 1.x can be found at https://github.com/ReactiveX/RxJava/blob/1.x/CHANGES.md
 
+### Version 2.0.0-RC3 - September 23, 2016 ([Maven](http://search.maven.org/#artifactdetails%7Cio.reactivex.rxjava2%7Crxjava%7C2.0.0-RC3%7C))
+
+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](https://github.com/ReactiveX/RxJava/wiki/What's-different-in-2.0#different-return-types) `Single` or `Maybe`.
+  - [Pull 4525](https://github.com/ReactiveX/RxJava/pull/4525) : Fixed generics of `combineLatest` and `zip` because `Function<? super T[], R>` doesn't work.
+  - [Pull 4522](https://github.com/ReactiveX/RxJava/pull/4522) : Fixed `delay` operator to call `onError` on the provided scheduler 
+  - [Pull 4490](https://github.com/ReactiveX/RxJava/pull/4490) : rename `isCancelled` to `isDisposed` inside the varios emitters of `create()`
+  - [Pull 4504](https://github.com/ReactiveX/RxJava/pull/4504) : add default `XObserver` implementation to `Single`, `Maybe` and `Completable`
+  - [Pull 4518](https://github.com/ReactiveX/RxJava/pull/4518) : add `ResourceXObserver` implementation to `Single`, `Maybe` and `Completable`
+  - [Pull 4536](https://github.com/ReactiveX/RxJava/pull/4536) : fix `timeout` operators not properly cancelling/disposing the upstream.
+  - [Pull 4583](https://github.com/ReactiveX/RxJava/pull/4583) : `Flowable.create()`'s `FlowableEmitter` didn't handle `null`s properly.
+  - [Pull 4586](https://github.com/ReactiveX/RxJava/pull/4586) : Add error assertion with predicate to `TestSubscriber` and `TestObserver`.
+
+In addition, the wiki page [What's different in 2.0](https://github.com/ReactiveX/RxJava/wiki/What's-different-in-2.0) has been extended with more information.
+
 ### Version 2.0.0-RC2 - September 5, 2016 ([Maven](http://search.maven.org/#artifactdetails%7Cio.reactivex.rxjava2%7Crxjava%7C2.0.0-RC2%7C))
 
 This Release Candidate features a large amount of internal fixes, cleanups and enhancements. Please refer to the [closed PRs](https://github.com/ReactiveX/RxJava/pulls?q=is%3Apr+is%3Aclosed+milestone%3A%222.0+RC+2%22) for its milestone. This includes the bugfix for the `Single.subscribeOn` failing with `Disposable already set!` error printed to the console ([Issue 4448](https://github.com/ReactiveX/RxJava/issue/4448), [Pull 4450](https://github.com/ReactiveX/RxJava/pull/4450)).