FlatSym test images

Hi James

I am busy evaluating the Flatness and Symmetry module. As part of that I was trying to run the test_basic.py test suite. It seems as though the directory of Flatness and Symmetry test images is missing on GitHub along with a couple of other images. Is it possible for you to upload these to your GitHub project.


Added: https://github.com/jrkerns/pylinac/commit/28929d77a761a6b9a4d7c2b260596cc643b0bd78