[Checkins] [zopefoundation/Zope] fe6253: Use travis-ci default distribution (now trusty).

[GitHub]

  Branch: refs/heads/travis
  Home:   https://github.com/zopefoundation/Zope
  Commit: fe6253eb63043bf1459c47e4ca2419a2dd85852a
      https://github.com/zopefoundation/Zope/commit/fe6253eb63043bf1459c47e4ca2419a2dd85852a
  Author: Hanno Schlichting <hanno at hannosch.eu>
  Date:   2017-09-09 (Sat, 09 Sep 2017)

  Changed paths:
    M .travis.yml

  Log Message:
  -----------
  Use travis-ci default distribution (now trusty).