Chartpress

essential for Helm 3 compatibility. The change is to prefix build number and
build hash with `n` and `h` respectively. The reason for doing this is that it
ensures we don't break the SemVer 2 assumption to not have a numerical segment
starting with zero, like for example `0.1.0-002.sdfg234` has with its `002`.
Helm 3 enforce this, while Helm 2 doesn't.

Fixes

- Prefix build info with n and h to ensure SemVer 2 validity, in order to solve Helm 3 compatibility [87](https://github.com/jupyterhub/chartpress/pull/87) ([consideRatio](https://github.com/consideRatio))

Added

- Add --force-build / --force-push, and don't let --tag imply it [70](https://github.com/jupyterhub/chartpress/pull/70) ([consideRatio](https://github.com/consideRatio))
- `helm dependency update` is now run as part of publishing, this ensures we honor requirements.yaml before publishing a chart [69](https://github.com/jupyterhub/chartpress/pull/69) ([consideRatio](https://github.com/consideRatio))

Fixes

- Fix regression to make a chart's `images` configuration optional again [77](https://github.com/jupyterhub/chartpress/pull/77) ([jacobtomlinson](https://github.com/jacobtomlinson))
- Fix regarding image paths as part of setting up thorough testing with PyTest [68](https://github.com/jupyterhub/chartpress/pull/68) ([consideRatio](https://github.com/consideRatio))

Maintenance

- Setup CD of PyPI releases on git tag pushes [83](https://github.com/jupyterhub/chartpress/pull/83) ([consideRatio](https://github.com/consideRatio))
- Adopt bump2version for automating version bumps [74](https://github.com/jupyterhub/chartpress/pull/74) ([minrk](https://github.com/minrk))

fixed was that charts published using `--publish-chart` replaced previous charts
in the helm chart repositories' `index.yaml` file that only differed by a SemVer
2 compliant build suffix like `+001.asdf123`. The bugfixes introduced in this
release avoid this issue, caused by a bug in helm, by using a build suffix of
`.001.asdf123` instead - a breaking change.

Example versions to expect in this release and onwards are given below where
some commits were made in between git tagged (`0.1.0` and `0.2.0-beta.1`)
commits.


without --long

- --long flag to always output build information in image tags and chart version [57](https://github.com/jupyterhub/chartpress/pull/57) ([consideRatio](https://github.com/consideRatio))
- Refactor publish_pages for comprehensibility [56](https://github.com/jupyterhub/chartpress/pull/56) ([consideRatio](https://github.com/consideRatio))

- Deprecate --commit-range [55](https://github.com/jupyterhub/chartpress/pull/55) ([consideRatio](https://github.com/consideRatio))
- Reset Chart.yaml's version to a valid value [54](https://github.com/jupyterhub/chartpress/pull/54) ([consideRatio](https://github.com/consideRatio))
- Don't append +build on tagged commits [53](https://github.com/jupyterhub/chartpress/pull/53) ([consideRatio](https://github.com/consideRatio))