Current version of SLEAP package.

This is used to set sleap.__version__, and it is also read by to set the version for the package (i.e., the version on PyPI).

The version should be manually updated before creating a new release, and then the release should be created with a tag matching the version number set here. For example, if you set the version to X.Y.Z, then the tag should be “vX.Y.Z”.

Must be a semver string, “aN” should be appended for alpha releases.