Bumped version to 1.0.4.

* Added `flake8` linter configuration.

* Made purely cosmetic changes in source accordingly.
* Added tools for package deployment.
* Switched build tool for documentation.
* Have different badges on PyPI/Read-the-Docs vs. GitHub.

* Removed superfluous reference data file.

* Minor changes to wording of documentation.

Version 1.0.1

* Released only to update meta info on PyPI.
* Added DOI badge to allow citations.

Release of version 1.0.0

* First release considered stable and ready for production.
* Removed speculation from implementation note regarding notation.

Release version 0.9.3

* Proofread and amended source-code comments.
* Minor changes to documentation build configuration.
* Removed some customization of the rendered HTML.

Release version 0.9.2

* Further improvements to documentation build scripts.

Release version 0.9.1

* Improved project meta information.
* Fixed documentation build issues on Read-the-Docs.

First version published to PyPI.

The release on PyPI was later yanked. That's because the version
number that the package declared was 0.9, not 0.9.0, so does not
strictly follow the semantic-versioning convention.