integrate alipay function #277
login to buy a course
connect login and signup page
add price for course, if price form is empty use 0
order page style
little changes
price can not be blank when edit course
progress bar style
now we define a function to decide who have watch auth
STEP1: author can set a video free
STEP2: paid user can watch all videos
STEP3: minor UI changes, ready to deploy
STEP4: show paid label
STEP4: bugfix1
STEP4: bugfix2
STEP4: bugfix3
Merge branch 'simple_auth'