Use package_data to install files under test and data

After some reading, I believe this is the best way to install the test scripts and data files in the same directory as the core code. It was a pain trying to figure out how to get the files from data_files in the same directory.

A side effect from pretending data is a module is that there is a warning, because there is no __init__.py in there. But, we cold create one if needed.