show_delta: 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 from 2.5.x up to and including 3.3.x.

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