kotlin extensions, api changes

Kotlin extension
Introduced Kotlin extension function test for Observable, Single, Completable and BlockingObservable.
Example: Observable.just("1").test().completed()

API change
Introduced has prefix to make API more natural. List of methods with new name
hasTerminalEvent
hasNoErrors
hasError
hasError
hasNoTerminalEvent
hasNoValues
hasValueCount
hasValues
hasValue
hasValuesAndClear

Initial release

RxTestWrapper covers all methods from TestSubscriber.For creation use one of static factory methods:

• RxTestWrapper<T> assertThat(Observable<T> observable)
• RxTestWrapper<T> assertThat(Single<T> single)
• RxTestWrapper<T> assertThat(Completable completable)
• RxTestWrapper<T> assertThat(BlockingObservable<T> blockingObservable)