Add attempeted at field in grading summary
add a function to get previous code
parse more info to _do_coding partial
auto restore previous code in training
fade out button after clicking run
split summary into 2 lines
add a new saved_at field in submission table
Add last save field to mission grading
Merge remote-tracking branch 'upstream/development' into features/mission-date
Merge branch 'features/mission-date' of https://github.com/wangqiang1208/coursemology.org into features/mission-date

Conflicts:
	app/views/assessment/gradings/_summary.html.erb
Merge pull request #200 from wangqiang1208/features/mission-date

Add attempeted at field in grading summary
remove unused code
use after_save to replace after_update and after_create
move js code to trainingsubmission.js
update achievement after grade changed
change user_course to student
modify code to support mutiple partials
 refine coding style
change hint text
make sure update_achievement ran before expire_fragment