Fix issue of 'text/x-rst' in README.rst
WARNING Error during upload. Retry with the --verbose option for more details.
ERROR HTTPError: 400 Bad Request from https://upload.pypi.org/legacy/
The description failed to render for 'text/x-rst'. See https://pypi.org/help/#description-content-type for more
information.
make: *** [release] Error 1