PyGriffin add distributed mesh option

closes #78 (closed)

Adds the option --distributed-mesh for running with Griffin. I added a test that is the same as the baseline test just to be sure that adding the option does produce the same results. However, I can't think of a better way to check that the --distributed-mesh option is actually passed (ie, could be getting a false positive on the test if the option is just never passed through). If you have an idea for checking that, I will added, otherwise this may be the best testing option.