Enabled strong_parameters across all models/controllers.

All models are now using ActiveModel::ForbiddenAttributesProtection, which shifts the responsibility for parameter whitelisting for mass-assignments from the model to the controller. attr_accessible has been disabled and removed as this functionality replaces that.

The require_parameters method in the ApplicationController has been removed in favor of strong_parameters' #require method.

It is important to note that there is still some refactoring required to get all parameters to pass through #require and #permit so that we can guarantee that parameter values are scalar. Currently strong_parameters, in most cases, is only being utilized to require parameters and to whitelist the few places that do mass-assignments.

app/models/topic_allowed_user.rb

@@ -1,7 +1,6 @@
 class TopicAllowedUser < ActiveRecord::Base
   belongs_to :topic
   belongs_to :user
-  attr_accessible :topic_id, :user_id
 
   validates_uniqueness_of :topic_id, scope: :user_id
 end