Add attempeted at field in grading summary
Allow line breaks in achievement descriptions (show as a list)
remove empty li(s)
remove chomp in the if statement
Using rich html editor to implement
put css style in custom.css.scss
Merge pull request #201 from wangqiang1208/features/achievements-list

Allow line breaks in achievement descriptions (show as a list)
Implement bulk download for missions
[migrations] remove and fix invalid migration files

db:migrate run without error for empty database
[Migration] remove old_tags table (no longer in use)
Merge pull request #202 from wangqiang1208/buggfixing/bulk-download

Fix bulk download for missions
Merge branch 'development' of github.com:Coursemology/coursemology.org into development
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
update achievement gain date to submission date(not grading date)
refine code
split summary into 2 lines
add a new saved_at field in submission table