zest.releaser entry point: commit the diff.

This is for the command line documentation that gets written during prerelease.
If you do not use zest.releaser, this code is never called.
Wrote command line documentation.
Preparing release 3.3.2
Back to development: 3.3.3
Merge remote-tracking branch 'origin/master'
changelog entry after merge
Appease check-manifest.