[Checkins] [zopefoundation/zope.publisher] 3366c3: Add support for Python 3.6

[GitHub]

  Branch: refs/heads/py36
  Home:   https://github.com/zopefoundation/zope.publisher
  Commit: 3366c36b40399ad3b81c6d80ffe9ac8fa4a7f31f
      https://github.com/zopefoundation/zope.publisher/commit/3366c36b40399ad3b81c6d80ffe9ac8fa4a7f31f
  Author: Jason Madden <jamadden at gmail.com>
  Date:   2017-04-21 (Fri, 21 Apr 2017)

  Changed paths:
    M .travis.yml
    M CHANGES.rst
    A setup.cfg
    M setup.py
    M tox.ini

  Log Message:
  -----------
  Add support for Python 3.6

Also add support for pip caching on Travis, and DRY with dependencies
in tox.ini.

Fix test_requires to be consistent. PyPy3.2 is no longer supported by
pip