Revert "Added isort to requirements"
Revert "Added isort to requirements"

isort is not really required for the project. And it actually caused
some weird problem, because of its dependency on pies, where pies==2.6.5
installed pies2overrides for Python 3.

This reverts commit 0cc993549ee585c59f2783d171d1d3074f7d60db.

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