Generalize to abstract output (e.g. `stderr.write`, `echo`) and also build-in repetitions via `reps` and emit range, mean, sdev(mean) stats.  Also, invert the `unit` usage so caller specifies the unit seconds, not the multiplier.
Generalize to abstract output (e.g. `stderr.write`, `echo`) and also build-in
repetitions via `reps` and emit range, mean, sdev(mean) stats.  Also, invert
the `unit` usage so caller specifies the unit seconds, not the multiplier.

c-blake/cligen