Cleanup ignored files when clearing docs
Cleanup ignored files when clearing docs

ellisonbg/nbgrader,modulexcite/nbgrader,jupyter/nbgrader,alope107/nbgrader,ellisonbg/nbgrader,modulexcite/nbgrader,ellisonbg/nbgrader,dementrock/nbgrader,EdwardJKim/nbgrader,EdwardJKim/nbgrader,jupyter/nbgrader,dementrock/nbgrader,jupyter/nbgrader,alope107/nbgrader,MatKallada/nbgrader,EdwardJKim/nbgrader,ellisonbg/nbgrader,MatKallada/nbgrader,jupyter/nbgrader,jhamrick/nbgrader,jdfreder/nbgrader,jhamrick/nbgrader,jupyter/nbgrader,EdwardJKim/nbgrader,jdfreder/nbgrader,jhamrick/nbgrader,jhamrick/nbgrader