Return failure status when tests fail.

Fixed
-----
* Fix the tests fail, return a failure status and don't run the
  coverage. This fixes a bug where failures were being masked by the
  success of unrelated commands run after the tests were run.
Merge remote-tracking branch 'upstream/master' into fix-run-travis-test
Changed to not build docs with tests.
Introduced a failed doctest for testing.
Fixed doctest.
Merge pull request #89 from mcflugen/fix-run-travis-test

Return failure status when tests fail.