Switch to using fixedRate() instead of fixedDelay() for Reactor

[lego-eden]

In BaseReactor I noticed that the method used to generate the Stream[IO, Command] of states is Stream.fixedDelay[IO]. Switching to using Stream.fixedRate[IO] might result in smoother motion with less microstutters. At least I expected the frames to be generated at a fixed rate and not with a fixed delay.

[noelwelsh]

Thanks!