restructure of model testing directories

[MikeLippincott]

          This comment pertains to the directory containing this file. Consider moving "test-focused" work to a dedicated area which isn't nested so deeply within this structure. Doing this might open up possibilities to perform other types of tests together and is often used as a pattern to help perform unit or functional tests for a project. It could also help avoid the calls for `sys.path.append("..")` below.

Originally posted by @d33bs in #25 (comment)