[Checkins] [zopefoundation/z3c.contents] eef3a3: Use zope.testrunner in tox

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/zopefoundation/z3c.contents
  Commit: eef3a3efdc330ea0c5a96f9fc3f5f02bab4177aa
      https://github.com/zopefoundation/z3c.contents/commit/eef3a3efdc330ea0c5a96f9fc3f5f02bab4177aa
  Author: Marius Gedminas <marius at gedmin.as>
  Date:   2015-11-05 (Thu, 05 Nov 2015)

  Changed paths:
    M tox.ini

  Log Message:
  -----------
  Use zope.testrunner in tox

Use setuptools extras instead of repeating the deps.  I think older versions of tox didn't support this syntax, which is why we have the smattering of duplicated depdencencies in zopefoundation's various tox.ini files.