- pull in multifold regression test from #134
- pull in more aggressive pulse tunings from #128
- remove all test sleeps related to old 1 second timestamps, so that
  things will break if old code is retained.
move away from timestamps to a per-run epoch counter for all keydir
mutations and iterations.  this adds 8 bytes per key, but it's better
to use slightly more memory than to be vulnerable to clock skews, and
gives us hard freezing boundaries to make folds work as they have
done traditionally.