Previously, distutils.version.LooseVersion was used, because it was
sort of close enough to how Alpine parses versions.
This new version uses the exact same algorithm, as `apk` does, and
it passes *all* of `apk`'s testcases for version checking (previously
we simply skipped the ones, that did not pass).
* Remove pmb/helpers/version.py left-over (it is in parse now)
* Make asserts consistent, do not use unnecessary parenthesis
Oliver Smith