The test assumes the threads would schedule in particular way, but they don't.
But what we really care to check is that we thread in the proper RL and it works.
We don't need to check that underlying queue impl works, that's done in its own tests.
So just verify these two things.
* Allow creating controller with custom RateLimiter.
Which was possible before via field modification.
Not switching to a builder pattern mostly for speed of resolution.
Happy to consider alternatives.
* Add tests for new functionality.
Specifically, these test that the Wait() function is notified about
the item, and that the RateLimiter is passed through to the queue.
* Add Options. Gophers love Options.
* Even moar controller GenericOptions.
* Attempt to appease lint, don't create struct for typecheck.
* GenericOptions -> ControllerOptions
* Public struct fields.
Dave Protasowski
Prashant Rewar
Victor Agababov
Jon Donovan