Version 4.0.0 declares itself as version 3.1.0 #101
Description
The packaged version 4.0.0 states that it is version 3.1.0: https://github.com/inveniosoftware-contrib/intbitset/blob/v4.0.0/intbitset/intbitset_version.py#L31 This might cause confusion and thus these version numbers should match everywhere.