Merge branch 'bowen' into rtong
Merge branch 'bowen' into rtong
fix bug with real data

fix lalala
fix null pointer
hello bowen
Merge branch 'rtong' into bowen
update button
expand and undo
change
first page undo complete

by now, no bugs found
add auto_assign_button

add 5 functions:
1. expand()
2. expandAll()
3. shrink()
4. shrinkAll()
5. undo_assign()
select madantory courses
fix some bugs
update database
update for UM
Merge branch 'bowen' into Bohan-Zheng

Conflicts:
	public/javascripts/action.js