It is a bit odd to use git tags for every release, when the code isn't
changing, it is just newer packages. Using GitLab's package registry[1],
means new releases can be uploaded without messing with git tags and it
is also a bit easier to purge old releases, which is needed to keep the
storage under control.

Old releases are purged after 90 days, which match the number of days
the releases are kept on the mirrors (6 releases are kept on the mirrors
and we are releasing biweekly).

[1] https://docs.gitlab.com/ee/user/packages/generic_packages/

Fix #118