`scheduleRec` for recursive scheduling (Scala)
Fixing a bug and a potential for other concurrency issues.
javadocs: add @see links to wiki discussion of "Backpressure"; add marble diagrams for onBackpressureFoo() operators
RxScala: Add retryWhen/repeatWhen methods

- Add example usage of retryWhen/repeatWhen to RxScalaDemo
Merge pull request #1555 from jbripley/rxscala-retrywhen

RxScala: Add retryWhen/repeatWhen methods
Merge pull request #1552 from abersnaze/most-recent-null

Fixing a bug and a potential for other concurrency issues.
Merge branch 'master' of https://github.com/Netflix/RxJava into docs
mergeMap generics

Fixes issue #1550
Merge pull request #1558 from benjchristensen/issue-1550

mergeMap generics
flatMap overloads

- migrate mapPair to use actual merge instead of reimplementing it
- deprecate mergeMap
Merge pull request #1560 from benjchristensen/flatMap-mergeMap

flatMap overloads
Merge pull request #1537 from GeorgiKhomeriki/master

recursive scheduling in RxScala
javadoc changes related to the mergeMap[Iterable] => flatMap[Iterable] changeover
Remove Variance on Defer

See https://github.com/Netflix/RxJava/issues/1157 for painful background.
Merge pull request #1561 from benjchristensen/issue-1157-defer

Remove Variance on Defer