* docs:
  * update doc/changes.rst, doc/format.rst
  * make sure appropriate ..versionadded:: directives are present
  * make sure docs are up to date
  * check coverage
  * cd doc; make html -- check that there are no warnings
* check MANIFEST.in
* update zs/version.py
* make sure there are no uncommitted changes
* clone a clean source directory
* in clean clone: python setup.py sdist --formats=zip
* test the sdist builds and passes tests (ideally in a clean venv,
  e.g., no cython):
     cd dist
     virtualenv t
     t/bin/pip install nose nose-progressive backports.lzma
     t/bin/pip install zs-*.zip
     t/bin/nosetests --all-modules zs
* twine upload dist/*.zip
* in original directory: git tag <version> && git push --tags
* Go to http://readthedocs.org/dashboard/zs/versions/, set the new
  version to build and update the default.
* announce release on:
     ...?
* update zs/version.py (add "-dev")
