Fixing regression test to do a more clever image diff.
Fixing regression test to do a more clever image diff.

For images we now use ImageMagik's compare tool rather than doing a
mere binary diff.

mfnch/pyrtist,mfnch/pyrtist,mfnch/pyrtist,mfnch/pyrtist,mfnch/pyrtist,mfnch/pyrtist