comments' model and controller
Merge branch 'develop' into nested_comments
Merge branch 'develop' into nested_comments
got the basic feature and styles for comments
finish the base feature of commenting system
fix a bug and remove some files that are of no use
add the feature of deleting comments
add the authorization for the operations on comments
fix a bug
improve the presentation of comments
improve the presentation of comments
improve the managing features for the comments
refine some pages' styles
refine some pages' styles
refine some pages' styles