Update release process to give guidance on updating the changelog prior to release.

docs/releases.txt

@@ -7,10 +7,20 @@ mechanical technique for releases, enacted by Travis following a
 successful build of a tagged release per
 `PyPI deployment <https://docs.travis-ci.com/user/deployment/pypi>`_.
 
+Prior to cutting a release, please check that the CHANGES.rst reflects
+the summary of changes since the last release.
+Ideally, these changelog entries would have been added
+along with the changes, but it's always good to check.
+Think about it from the
+perspective of a user not involved with the development--what would
+that person want to know about what has changed--or from the
+perspective of your future self wanting to know when a particular
+change landed.
+
 To cut a release, install and run ``bumpversion {part}`` where ``part``
 is major, minor, or patch based on the scope of the changes in the
 release. Then, push the commits to the master branch. If tests pass,
-the release will be uploaded to PyPI (from the Python 3.5 tests).
+the release will be uploaded to PyPI (from the Python 3.6 tests).
 
 Release Frequency
 -----------------