Investigate test tolerances

[erykoff]

It seems that the test tolerances may be too loose in that #20 passed when there seems to be a significant change.

[kadrlica]

I'll note that the footprint image tests all failed on my machine. I guess that this was because my matplotlibrc file differed from what you were using. While checking the images is neat, I'm not sure it is really reproducible for a bunch of developers.

[erykoff]

That part I just fixed on c537275