how to do the end of term marks (so i dont forget again)

1. put the exported marks from the gradebook in raw_marks.csv
2. Rscript clean_marks.R   <- fixes the blank cells and the late penalty
3. Rscript make_report.R   <- makes the final sheet

then check grades_final.csv by hand and send it to the exams office. i fix a few by hand
after moderation so dont lose those!!