Add setuptools.setup long_description

[bjlittle]

Add a long_description to setuptools.setup in setup.py in order to provide a relevant description to users on for PyPI stratify e.g.,

def long_description():
    fname = os.path.join(PACKAGE_DIR, 'README.md')
    with open(fname, 'rb') as fi:
        result = fi.read().decode('utf-8')
    return result
...
setup_args = dict(
...
    long_description=long_description(),
    long_description_content_type='text/markdown',
...

Something along those lines...

Then see how it's rendered on https://test.pypi.org/