test config: update: pytest 2.7.0, pytest-xdist 1.12
test config: update: pytest 2.7.0, pytest-xdist 1.12

tomviner/pytest-django,ktosiek/pytest-django,RonnyPfannschmidt/pytest_django,davidszotten/pytest-django,aptivate/pytest-django,thedrow/pytest-django,ojake/pytest-django,felixonmars/pytest-django,pelme/pytest-django,pombredanne/pytest_django,bforchhammer/pytest-django,hoh/pytest-django,reincubate/pytest-django