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) that contains the raw PR description as the tag message.
7. Create a GitHub release based on this tag; this should then automatically deploy to PyPI.