Compute in contrast, add contours.

Signed-off-by: David Brainard <brainard@psych.upenn.edu>
Save a figure at the end.  Make some diagnostic plots optional.

Signed-off-by: David Brainard <brainard@psych.upenn.edu>
Little comment fussing.

Signed-off-by: David Brainard <brainard@psych.upenn.edu>