Tweak bulk_kinematic_sim test

Don't accept char input at the end of test, remove "naive"
implementation. Turns out that approach might be a bit better;
cachegrind showed a 1.0% miss rate with it as opposed to the 2.3%
miss rate with the current implementation. I'm unfamiliar with
cachegrind and memory optimization though, but for the time being
we'll leave it as is.