TST: Add test that leverages `verification.py`

[nawtrey]

There are many testing recommendations in #3 that are covered in the verification script verification.py. Simply adding a test that executes this script will improve the rigor of the testing suite, as the verification script tests randomly generated diagrams.

Considerations

1. The verification script uses Multibind to handle the creation of the rate matrices for the randomly generated diagrams, so this will have to be installed to run the script.