Hi all,

I made a pull request proposing a fix for this issue. There is still quite a lot to be done:
 - I exposed some variables (and probably methods too) that used to be hidden;
 - I did not update the documentation;
 - I did not add a proper test.

I will try to fix those by the end of the week.

The patch mainly consists of two things:
 - having Path (resp. PurePath) be a variable pointing at either (Pure)PosixPath or (Pure)WindowsPath, depending on the platform (like Kevin Norris suggested);
 - introducing two new abstract classes _PurePath and ConcretePath from which PurePosixPath, PureWindowsPath and PosixPath, WindowsPath classes inherit;
 - removing the _Flavor classes, and redistributing their method to platform-specific classes.

Ideally I would like _PurePath to become a public class, but I could not come up with a proper name. Any feedback is more than welcome =]