Add missing semver package to package requirements

[frenck]

fixes #7

[bouwew]

Looking at this: 6b4bdc3 it needs to be: semver ==2.13.0

[frenck]

Sounds not good. Libraries should never strict pin requirements in their package. I think you are misunderstanding the lock file construct used here.

[bouwew]

After further reading I found out that semver.compare is depreciated so better to fix this: python-semver/python-semver#236 (comment)

I've done some more reading, semver.compare is not depreciated so the proposed change should fix the issue.

@ManneW please test and merge this PR, and release and update the vilfo-integration.

As far as I can see it's about the semver.compare use, that's the link to the specific semver version.
If the version-number should not be used then the relevant code needs some reworking I'm thinking.