SemVer semantic: 7.0.0-rc1 > 6

[maowtm]

Currently semver_geq("7.0.0", "6") is true but semver_geq("7.0.0-rc1", "6") is false (due to the semver crate always returning false when comparing pre-release with non-pre-releases). Need fix.

[maowtm]

This may actually require either finding another semver crate or writing our own semver implementation... So before we move on @mechtaev can we discuss the exact semantic we want for semver_*...?

[mechtaev]

The official website has a specification: https://semver.org/. I have not seen anything there that forbids comparing pre-release with non-pre-releases, so it seems like a bug to me.