* docs:
  * update doc/changes.rst
  * make sure appropriate ..versionadded:: directives are present
  * make sure docs are up to date
  * verify that the ">97% coverage" claim in overview.rst is still true.
  * cd docs; make clean html -- check that there are no warnings
* check MANIFEST.in
* update version in doc/changes.rst, patsy/version.py
* make sure there are no uncommitted changes
* clone a clean source directory (so as to get a clean checkout
  without killing the expensive-to-recreate .tox dir)
* python setup.py sdist --formats=zip
* unzip sdist to a clean directory, and run tox in it
* in original directory: git tag v<version> && git push --tags
* in clean clone: python setup.py sdist --formats=zip && python setup.py bdist_wheel
* twine upload dist/*.zip dist/*.whl
* announce release on:
  pydata@googlegroups.com
  pystatsmodels@googlegroups.com
  scipy-dev?
  pypi
* update version in patsy/version.py again
* go to https://github.com/pydata/patsy/releases/new and type the tag
  name and give it some text. (This will trigger Zenodo archiving the
  tag.)
