Update README to minimize interface duplication
Update README to minimize interface duplication

ellisonbg/nbgrader,jupyter/nbgrader,jhamrick/nbgrader,jhamrick/nbgrader,jupyter/nbgrader,EdwardJKim/nbgrader,ellisonbg/nbgrader,jupyter/nbgrader,EdwardJKim/nbgrader,EdwardJKim/nbgrader,ellisonbg/nbgrader,jupyter/nbgrader,jhamrick/nbgrader,ellisonbg/nbgrader,jhamrick/nbgrader,jupyter/nbgrader,EdwardJKim/nbgrader