automation in our changelog?

It might be nice to add some automation in our changelog to either:
- make it easier to roll up changes since the last release, using the git commit log and common commit message patterns, or
- have a tool / git commit hook / travis script to encourage people to update the changelog for every PR

Start by choosing between rolling up changes from the git commit log and encouraging changelog updates for every PR. Review the repository's changelog and current PR workflow, then define the commit-message patterns or update checks the chosen approach would use. Done means the selected automation is specified and consistently supports changelog maintenance.

Written by the indexing model from the issue text.