Partial versions improvement

I think I have fixed the issue where the version '1.2' became '1.2.None'. Now it becomes '1.2.x', which I think is somewhat better. I also considered '1.2.*', but quick and superficial googling appeared revealed 'x' to be more common.

I also added tests to make sure we don't break this in the future.

I am a little unhappy with the long lines (35, 36), but it works and removes the need for access methods (which I tried but found ugly).

As usual, comments and feedback welcome :)