Fix issue #15. Package 'path' is not OS aware, while 'filepath' is.

Squashed commit of the following:

commit 50e4ca5d2d1e33d2ddbe73907f51e79f80df2795
Author: Antoine Grondin <antoinegrondin@gmail.com>
Date:   Wed Nov 6 15:23:22 2013 -0500

    Use OS-aware path manipulations, instead of OS-agnostic "path".

commit 170ecdb12c491602e5b8c1d580d5d33545bb4c7a
Author: Antoine Grondin <antoinegrondin@gmail.com>
Date:   Wed Nov 6 14:37:52 2013 -0500

    Use os.PathSeparator for every use of '/'