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* Renamed to ``readme_renderer``: https://github.com/pypa/readme_renderer
to work around an name overlap with ``README`` files shipped in Python's
default site-packages directory on certain case-insensitive file systems.
* Added `PyPA Code of Conduct`_.
* Allow <sub> and <sup> tags when cleaning rST HTML output.
* Dropped support for Python 2.6.
.. _PyPA Code of Conduct: https://www.pypa.io/en/latest/code-of-conduct/