add long_description for pypi

[mundanevision20]

Hi @radomirbosak

thanks for merging my PR (#157) so quickly.

After spotting the release over at pypi I thought I'd might be helpful to add a long_description -> README.md to the pypi project page.

I also slighty updated the code syntax to use pathlib instead of os.

Regards, Hennig

[radomirbosak]

Hi @mundanevision20 , I tested your PR on test pypi and it looks really good :)
Thank you!

Pathlib seems to work with python 3.4 and newer

So I'll just remove the python 3.3 support from setup.py

In any case, let me merge this first.

[radomirbosak]

Released as 0.17.0 🎉

GH: https://github.com/radomirbosak/duden/releases/tag/0.17.0
PyPI: https://pypi.org/project/duden/0.17.0/