Creating and deploying a release

The process for creating a release is the following:

1. On a local branch at the head of master, use invoke setver --new-ver <version> to create a new release with the appropriate version. If you are preparing a patch release, simply use invoke setver --patch to bump the minor version.
2. Use invoke update-openapijson to generate the Open API schema with the new (semver) version number.
3. Commit the changes from steps 1 and 2 and push the branch to GitHub.
4. Create a PR that contains only the version bumping commit and make an effort to summarize all changes since the last version, broken down by new features, updates and bug fixes (for a complete example, see #251.
5. Once the PR has been reviewed, it can be rebased/squashed onto master.
6. Create a git tag on the new head of master (i.e. after the PR has been merged) with the new version number as the tag name, with the raw PR description as the tag message.
7. Create a GitHub release based on this tag; the description can be left blank, as GitHub will use the tag message. This will then trigger an automatic deployment to PyPI.