This issue tracks the new, Java 8-related operators to be implemented.

• Flowable.fromOptional
• Flowable.fromStream
• Flowable.fromCompletionStage
• Flowable.mapOptional
• Flowable.collect(Collector)
• Flowable.firstStage
• Flowable.singleStage
• Flowable.lastStage
• Flowable.firstOrErrorStage
• Flowable.singleOrErrorStage
• Flowable.lastOrErrorStage
• Flowable.blockingStream + 1
• Flowable.flatMapStream + 1
• Flowable.concatMapStream + 1

• Observable.fromOptional
• Observable.fromStream
• Observable.fromCompletionStage
• Observable.mapOptional
• Observable.collect(Collector)
• Observable.firstStage
• Observable.singleStage
• Observable.lastStage
• Observable.firstOrErrorStage
• Observable.singleOrErrorStage
• Observable.lastOrErrorStage
• Observable.blockingStream + 1
• Observable.flatMapStream
• Observable.concatMapStream

• Maybe.fromOptional
• Maybe.fromCompletionStage
• Maybe.mapOptional
• Maybe.toCompletionStage() + 1
• Maybe.flattenStreamAsFlowable
• Maybe.flattenStreamAsObservable

• Single.fromCompletionStage
• Single.mapOptional returns Maybe<T>
• Single.toCompletionStage()
• Single.flattenStreamAsFlowable
• Single.flattenStreamAsObservable

• Completable.fromCompletionStage
• Completable.toCompletionStage

• ParallelFlowable.mapOptional
• ParallelFlowable.flatMapStream
• ParallelFlowable.collect(Collector) returns Flowable