python setup.py test doesnt run the tests

```console
> python setup.py test
/home/jayvdb/.asdf/installs/python/3.6.7/lib/python3.6/distutils/dist.py:261: UserWarning: Unknown distribution option: 'long_description_content_type'
warnings.warn(msg)
running test
running egg_info
writing cli_helpers.egg-info/PKG-INFO
writing dependency_links to cli_helpers.egg-info/dependency_links.txt
writing requirements to cli_helpers.egg-info/requires.txt
writing top-level names to cli_helpers.egg-info/top_level.txt
reading manifest file 'cli_helpers.egg-info/SOURCES.txt'
reading manifest template 'MANIFEST.in'
writing manifest file 'cli_helpers.egg-info/SOURCES.txt'
running build_ext

----------------------------------------------------------------------
Ran 0 tests in 0.000s

OK
```

setup.py needs `tests_require`, and override the test loader to be `pytest`, etc.