[Checkins] [zopefoundation/zope.i18nmessageid] 19f779: Use extras=test in tox.ini. [skip ci]

[Jason Madden]

  Branch: refs/heads/deprecated-setuptools-features
  Home:   https://github.com/zopefoundation/zope.i18nmessageid
  Commit: 19f779725f062928c121e0383231a8a22d01a8c5
      https://github.com/zopefoundation/zope.i18nmessageid/commit/19f779725f062928c121e0383231a8a22d01a8c5
  Author: Jason Madden <jamadden at gmail.com>
  Date:   2020-01-20 (Mon, 20 Jan 2020)

  Changed paths:
    M tox.ini

  Log Message:
  -----------
  Use extras=test in tox.ini. [skip ci]

Per https://github.com/zopefoundation/zope.i18nmessageid/pull/19#discussion_r368547455 from @mgedmin