BLD: ALL Travis CI tests are running on Python 3.5
Look at any one of the Travis CI builds at https://travis-ci.org/pandas-dev/pandas

All builds are running on Python 3.5.3.  Even the builds that are marked 2.7 and 3.6 are running on Python 3.5.3.  Either I am missing something or there seems to be a configuration issue between tox.ini and .travis.yml.