RxJavaPlugin Unit Tests

Attempt to fix non-determinism https://github.com/Netflix/RxJava/issues/329
Made unit tests work on private instances in each test rather than against static global.
Improve testNoBufferingOrBlockingOfSequence determinism

Removed use of Thread.sleep to fix non-determinism issue reported in https://github.com/Netflix/RxJava/issues/329
Improve testRecursiveScheduler2 determinism

Removed use of Thread.sleep and changed assertion to allow for the expected race condition between the counter loop and unsubscribe event to fix non-determinism issue reported in https://github.com/Netflix/RxJava/issues/329
Improve determinism of GroupBy.testUnsubscribe

Increased delta value from 2 to 10 to try and resolve issue reported in issue https://github.com/Netflix/RxJava/issues/329
Make Materialize.testMultipleSubscribes test deterministic

Refactored to use BlockingObservable instead of non-blocking subscribe and waiting on the underlying thread (it was only waiting on one of two threads running).
This should resolve one of the issues reported in http://github.com/Netflix/RxJava/issues/329
Merge pull request #332 from benjchristensen/issue-329-unit-tests

Issue 329: Fix non-deterministic unit tests