diffconfig: Update script to support python versions 2.5 through 3.3

Support past and active versions of python while maintaining backward
compatibility. Script has been tested on python versions up to and
including 3.3.X.

Signed-off-by: Mike Pagano <mpagano@gentoo.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>