Moving to CalVer for our versioning

[thinkl33t]

AFAIK we're never going to support an older version of the badge firmware, and our response to anyone who has an issue with one will be that they should update to the latest and try first

This pushes me fairly heavily towards moving our releases to be calver - so the releases would be something like YYYY.MM.MICRO

this means we don't have to worry as much about semantics and having 'enough' things to push a new release - we can just push a release when we want.

[MatthewWilkes]

Fine by me, I generally prefer calver. I do think we need to be careful about breaking changes on event years, but we don't need semver to do that