fixed index bug caused by single collection inheritance

models/comment_thread.rb

@@ -3,11 +3,9 @@ require_relative 'content'
 class CommentThread < Content
   include Mongo::Voteable
   include Mongoid::Timestamps
-  include Mongoid::TaggableWithContext
-  include Mongoid::TaggableWithContext::AggregationStrategy::RealTime
+  
 
   voteable self, :up => +1, :down => -1
-  taggable separator: ',', default: []
 
   field :comment_count, type: Integer, default: 0
   field :title, type: String

models/content.rb

 class Content
+
   include Mongoid::Document
+  include Mongoid::TaggableWithContext
+  include Mongoid::TaggableWithContext::AggregationStrategy::RealTime
+
+  taggable separator: ',', default: []
 
   def author_with_anonymity(attr=nil, attr_when_anonymous=nil)
     if not attr