tox / travis / coverage support
added pypy to tox environments
python 2.6 needs an explicit index in formatting strings
explicitly setting 1 level of relative imports in gathering test modules

-1 doesn't work on python 3.3+
Merge pull request #5 from robdennis/master

adding tox / travis / coverage support; fixing python 2.6 test bug
Merge branch 'master' of github.com:ftobia/pytest-ordering into develop