small wording change
fixed save and close error
session codes
time spent feedback on session preps
more generous thresholds for computing time spent in prep for sessions
alternate way to get credit for session prep with 20 minutes of activity
improved feedback on session preps
remove extraneous prints
allow credit if they did enough activities, even after the class started
Merge branch 'pip' of https://github.com/presnick/runestone into pip
added line to make sure score.points is always numeric OR 0