Moving humanized_content_type from DocumentablesHelper to Document model. Removing humanized_file_size in favor of direct use of number_to_human_size form ActionViewHelper. Added additional documentens to all concerned views

app/models/document.rb

@@ -52,6 +52,10 @@ class Document < ActiveRecord::Base
     end
   end
 
+  def humanized_content_type
+    attachment_content_type.split("/").last.upcase
+  end
+
   private
 
     def documentable_class