Use py.test command for consistency with nupic unit and integration tests
Update README. py.test is already a nupic dependency.
Merge remote-tracking branch 'upstream/master' into use-py.test
Limit test discovery to tests/ for consistency w/ nosetests behavior
Make README.md consistent with .travis.yml
Merge pull request #1 from oxtopus/use-py.test

Use py.test