[Checkins] [zopefoundation/zope.interface] fbe3d5: Enable coveralls

[GitHub]

  Branch: refs/heads/coveralls-on-travis
  Home:   https://github.com/zopefoundation/zope.interface
  Commit: fbe3d51b0b4d7ecf3282548fe77afc19482dcf48
      https://github.com/zopefoundation/zope.interface/commit/fbe3d51b0b4d7ecf3282548fe77afc19482dcf48
  Author: Jason Madden <jamadden at gmail.com>
  Date:   2017-06-09 (Fri, 09 Jun 2017)

  Changed paths:
    M .travis.yml

  Log Message:
  -----------
  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.