throttle-promises expectedHistory seems to be wrong about exercises

[jcready]

The expected history is correct the way it is. What you listed as your expected history would mean that 5 promises get executed and another 5 won't start until those original 5 have all resolved (which isn't correct). What should happen (and what is correctly being tested already) is that 5 promises get executed right away and as soon as any one of them resolves, another one gets started.

While your solution might only execute a 5 promises at a time (which is correct), it is much less efficient than it could be. Your solution is averaging ~2.5 running promises at any given time while the optimal solution (and what is already being tested) is averaging ~4.5 running promises.