Revert "CompositeException does not mutate nested exceptions by attaching stacks, but instead"

This reverts commit f4ae92aa624923e9a632fb677730a2d6e04595e5.
Remove cycles in CompositeException
Move cast to parent function
Remove cast
Remove unused imports/locals
Add generics
Add generics
Correct static access warnings
Adding alt attributes to img tags in javadocs to avoid occasional build issues
minor javadoc improvements
Fix Merge Bug

Working on https://github.com/Netflix/RxJava/issues/1420
Merge pull request #1442 from benjchristensen/merge-bug

Merge Bug
Infinite request with Long.MAX_VALUE instead of -1

Migrating to this after discussions at https://github.com/reactive-streams/reactive-streams/issues/62
Merge pull request #1443 from benjchristensen/request-long-max-value

Infinite request with Long.MAX_VALUE instead of -1
[Gradle Release Plugin] - pre tag commit:  '0.20.0-RC1'.
[Gradle Release Plugin] - new version commit:  '0.20.0-RC2-SNAPSHOT'.
Version 0.20.0-RC1
first pass at javadocs for new backpressure stuff
Zip with Backpressure Support

This supports both upstream and downstream backpressure.
RxScala: Add Scala idiomatic methods