force reading README.md in utf-8

[bollwyvl]

This updates the setup.py to be more robust vs. non-utf-8 locales (such as the default on windows).

noted on:

• add jsf 0.4.0 conda-forge/staged-recipes#20888
  • logs

As a noarch package, this won't be a long-term issue, but for the initial build we like to make sure everything works on the "big three" advertised platforms.