Minor fix needed for setup.py for Windows environments.

[jeruyyap]

There is minor issue with this package in Windows environments that causes installation to fail due to the encoding not being specified for the README file in setup.

A quick fix that comes to mind for this would be to specify utf8 when opening the README in the setup.py:
with open('README.rst', encoding='utf8') as readme_file:

This seems to be an issue in 2.3.0 but not in 2.2.4.

[kangelovv]

I hit this as well, on Debian Buster.