twine check error in 0.8.1

[codekiln]

$ twine check dist/django-elastic-migrations-*.tar.gz
/Users/pnore/.virtualenvs/dem3/lib/python3.7/site-packages/readme_renderer/markdown.py:38: UserWarning: Markdown renderers are not available. Install 'readme_render[md]' to enable Markdown rendering.
  warnings.warn(_EXTRA_WARNING)
Checking distribution dist/django-elastic-migrations-0.8.1.tar.gz: Failed
The project's long_description has invalid markup which will not be rendered on PyPI. The following syntax errors were detected:
line 460: Warning: Title underline too short.

0.8.1 (2018-11-19)
^^^^^^^^^^^^^^^^^

good grief, this is pretty exact checking, but it causes the rst rendering to fail hard: https://test.pypi.org/project/django-elastic-migrations/0.8.1/. Fix this and add a twine check step to the "Cutting a New Version" steps in the readme.