Summary: pytest plugin to help with testing figures output from Matplotlib

Description:
This is a plugin to facilitate image comparison for Matplotlib in pytest. For
each figure to test, the reference image is subtracted from the generated
image, and the RMS of the residual is compared to a user-specified tolerance.
If the residual is too large, the test will fail (this is implemented using
helper functions from matplotlib.testing).

Maintainer: papoteur