[Checkins] [zopefoundation/zope.interface] e6b6ba: Enable coveralls (#89)

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/zopefoundation/zope.interface
  Commit: e6b6ba2181e2265fa814a34a119531b1ddca23bf
      https://github.com/zopefoundation/zope.interface/commit/e6b6ba2181e2265fa814a34a119531b1ddca23bf
  Author: Jason Madden <jason+github at nextthought.com>
  Date:   2017-06-09 (Fri, 09 Jun 2017)

  Changed paths:
    M .travis.yml

  Log Message:
  -----------
  Enable coveralls (#89)

* Enable coveralls

Test coverage is not at 100% yet so it should fail this PR.

Also enable pip caching since we are installing more deps.

Update PyPy versions to latest available for speed and because the old
version of PyPy3 can't install newer pip and coverage, etc.

Partially addresses #87

* Even newer pypys

* Despite the list, pypy-5.6 doesn,t work, it must be 5.6.0