Revision of JMH Tests

- removal of all non-JMH perf tests
Merge pull request #1376 from benjchristensen/jmh

Revision of JMH Tests
Update README.txt
Disable flatMapTwoNestedAsync for now

it runs out of memory in JMH
1000000 is too much

... for these tests.
Enable FlightRecorder for JMH Tests
BugFix: Pivot Concurrency
Parallel Operator Rewrite

A rewrite of the `parallel` operator that is more efficient by not using `groupBy` and ready to support backpressure.
Merge pull request #1378 from benjchristensen/pivot

BugFix: Pivot Concurrency
Merge pull request #1379 from benjchristensen/parallel

Parallel Operator Rewrite
TakeUntil & NotificationLite

A rewrite of TakeUntil that doesn't leak NotificationLite.COMPLETE outside of itself. It causes problems to leak the sentinels as other operators also using NotificationLite get confused.
Remove unnecessary code
OnSubscribe: DelaySubscribe -> UnsafeSubscribe

This could cause an unwanted unsubscribe to be propagate because of the `SafeSubscriber`
Formatting
TestSubscriber.assertNoErrors
TrampolineScheduler Cleanup

Remove the null check and lazy creation, build the queue in the ThreadLocal. Fix bugs about "work in progress".
Merge pull request #1380 from benjchristensen/fixes

Variety of Fixes
Adding missing javadocs to TestSubscriber (#1322)
Adding missing javadocs to TestSubject (#1322)
Adding missing javadocs to Exceptions/OnErrorThrowable (#1322)