welcome mail
adjust reseting user password style
course show style
playlist style block
make number label center in vertical direction
correct a typo
Merge pull request #402 from happypeter/course_show_page

Course show page
use svg for circle #403
change comment content from string to text #404
videos and courses description type changes #404
Merge pull request #405 from happypeter/comment_content_type

Comment content type
Merge pull request #388 from happypeter/send_mail

Send mail
for new route
get video aspect ratio
deal with blank video ratio
show video height in term of video ratio
Merge pull request #412 from happypeter/video_ratio

Video ratio
user can't access an unpublished course except its owner
nice color for comment preview box border
update luckyyang avatar