add spec for videos controller and users controller
supress I18n validation deprecation warning
add spec for sessions controller, and refactor all controllers to use fabricator
add migration and spec for review model
implement review video feature
refactor the seed file
implement the average rating method in video
implement the average rating method in video
Merge branch 'mod3' of https://github.com/fanchenpai/myflix into mod3
hide average rating when no reviews
improve fabricators and seed file