tox: - added dependency on unittest2 for py26
Merge pull request #45 from AvdN/tox

tox: - added dependency on unittest2 for py26
Merge github.com:kislyuk/argcomplete into travis-unittest2
travis-unittest2: added unittest2, use mirrors

--use-mirrors is recommended http://about.travis-ci.org/docs/user/languages/python/#Pre-installed-packages

- added 2.6 and test in yaml