Unit test to assert correct scheduler thread
Update Observable.java

from(scheduler) -> add diagram, standardize javadoc comments
range(scheduler) -> add diagram, standardize javadoc comments
startWith(scheduler) -> add diagram, standardize javadoc comments
Refactored ObserveOn without ScheduledObserver
Merge pull request #499 from benjchristensen/observeOn-refactor

ObserveOn Refactor