Fixes #153.
Update existant evolve steps.
Add myself to contributors.
Fix up evolve step.
Fix evolve steps that were missed on first pass.
Fix up last remaining steps.
Change the argument order of evolve logic functions to be root, registry.

Added explicit tests that call an "evolve logic function" with the new API,
and without (supporting BBB).
Issue a warning (via the stdlib warnings module) when an evolve logic function
is detected as taking only one argument.
Update narrative docs.
Merge pull request #233 from mgrbyte/evolve-steps-accept-registry

Fixes #153.
rename defer-until-commit to at-commit in UI for less confusion