add late submission penalty to SubmittedAssignment db api add late submission penalty to SubmittedAssignment dict repr
add late submission penalty to SubmittedAssignment db api
add late submission penalty to SubmittedAssignment dict repr

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