RxScala: Fix recursive onStart call in Subscriber
Deprecate ParallelMerge

Removing in 1.0 as it is confusing and rarely useful.
Merge pull request #1646 from benjchristensen/deprecate-parallel-merge

Deprecate ParallelMerge
Merge pull request #1641 from jbripley/rxscala-onstart-recursive

RxScala: Fix infinite recursive onStart call in Subscriber