Add changelog to repo and release notes to documentation

[jordaneremieff]

Since I'm actually adding notes to the releases now I think this should be included in the repo itself and not just the GitHub release. I wonder if there is a good way to automate this so content can be reflected in all three places (releases.md, CHANGELOG.md, Github release).

[jordaneremieff]

I've added this manually for now, but probably want to automate this as part of the release process