this isn't testing anything except that the function returns basically anything, and I don't think this functionality warrants a whole package anyway. 

We already have `Repeat(x, fn)` in benchmarker.go, and we have `ExecuteConcurrently` and `Execute` to execute arbitrary channels of functions. How about we just create a `RepeatEveryUntil(seconds, stopTime, fn)` method in benchmarker.go similar to the existing `Repeat(x, fn)` and use that? 

In the test for that, let's test that it sends the function 'fn' to the returned channel the number of times you'd expect given the stopTime and the amount of seconds between repetitions, and that the times between repetitions are (approximately) what we expect.