Fix this fragile unit test.  Also made the call to stop updating the clock automatically block until the thread which updates the clock is ensured to stop
These unit tests were not correct, we should be calling shutdownNow in order to verify like this
Put a delay of 1 millisecond here, in case we have a slow system timer, to ensure that the shutdown task goes after all currently scheduled tasks.
Added ability to get a count of how many runnables/callables are scheduled or awaiting execution
This class does not really belong in testing.  Concurrent is not even the best match for it, but for not it seems a lot better than the test package.

I also updated it so that it is returning the ListenableFuture.
Expansion to this javadoc
Merge branch 'master' into experimental-more_concurrent_scheduler