url_validator.rb, fix a problem of without a validate_each funtion
Gemfile and Gemfile.lock, add gem 'cancan' and 'rolify'
role.rb, new  file rolify role model
user.rb, implement rolify
rolify.rb, new file rolify_initializer
schema.rb, change schema when 'rake db:migrate'
migrate_file, new file generated when 'rake db:migraet'
ability.rb, new file cancan Ability model
application_controller.rb, redirect cancan exception to root page
controller_about_manage, use cancan authorization
url_validator.rb, modify it beacause it is empty file
Merge pull request #26 from garylai1990/feature/cancan

Feature/cancan