[Checkins] [zopefoundation/zope.publisher] 422fea: Add support for Python 3.6

[GitHub]

  Branch: refs/heads/py36
  Home:   https://github.com/zopefoundation/zope.publisher
  Commit: 422fea392ef8497bb3824db5d4f290976a0a0420
      https://github.com/zopefoundation/zope.publisher/commit/422fea392ef8497bb3824db5d4f290976a0a0420
  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.