Naive schedulers implementation
Added ScheduledExecutorServiceScheduler
Added to Schedulers
More tests
Headers
ObserveOn/SubscribeOn unit tests
Some documentation
Documenting code
renamed tests
Extracted ScheduledObserver as a separate class
Simplified ImmediateScheduler
Removed SleepingAction from Abstract scheduler.
ExecutorScheduler throws exception for the delayed action.
added threadPoolForComputation and threadPoolForIO schedulers
Merge branch 'schedulers' of git://github.com/mairbek/RxJava into schedulers-merge

Conflicts:
	rxjava-core/src/main/java/rx/Observable.java
Keeping ScheduledObserver out of public API

For now keeping ScheduledObserver an implementation detail until it's clear we want it part of the long-term public API.
Formatting to match codebase
Consolidating ExecutorScheduler and ScheduledExecutorScheduler

ScheduledExecutorScheduler is just an extension of ExecutorScheduler so keeping them together for less surface area on the API.
Make ForwardingScheduler Internal

Until there is a use case other than unit testing I'm moving this to a non-public role so it's not part of the public API.
Tweaks to Executor/ExecutorScheduler/IOScheduler and Javadocs

- added Javadocs
- moved some classes to package-private until they are proven necessary for the public API
- made ExecutorScheduler support Executor implementations and still work with time delays by using a system-wide scheduler/timer
- made IO thread-pool unbounded with a cached thread pool
Basic unit tests

- I plan on using this to expand unit testing around various aspects of schedulers
- this is not done as an inner-class as it does not correlate with just one class but is cross-functional over many classes thus it fits best here