Include the `long_description` field for easier searching in PyPi

The current `setup.py` field does not populate a description field for the project. As a result, the PyPi page for it shows no description.

If possible, please include this field so that user's have an easier time understanding what the project is all about. :)

Relevant docs: https://packaging.python.org/guides/making-a-pypi-friendly-readme/