Add onErrorFlatMap to RxScala
Add nest to RxScala
Add flatten variant to RxScala
Add switchMap to RxScala
Add retry variant to RxScala
Add error variant to RxScala
Add foreach to RxScala
Add combineLatest variant to RxScala
Add orElse to RxScala
Update CompletenessTest.scala
Add groupByUntil variant to RxScala
Add groupJoin to RxScala
Add pivot to RxScala
Add longCount to RxScala
Add toMultimap to RxScala
Update pivotExample
Rewrite toMultimap
Replace unnecessary with details
Change the return type, and add tests
comments, docs and names improvement