Semantic Versioning

Originally, I wanted to start the same versioning scheme here I had initiated for bitte cli, which was the semver semantic. At the time, it was argued that calendar version may be more appropriate, and that's what was initiated.

However, now that we are maintaining release branches for patches and hot-fixes, it really seems that semantic versioning would be more appropriate. Adding additional commits to a date versioning release kind of destroys the meaning of the version, and the patch release number `x.x.[0-9]` seems more appropriate for that kind of thing.