added created_at to comments/index

Author: scarver2

config/locales/en.yml

@@ -72,6 +72,7 @@ en:
       labels:
         destroy: "Delete"
     comments:
+      created_at: "Created"
       resource_type: "Resource Type"
       author_type: "Author Type"
       body: "Body"

lib/active_admin/orm/active_record/comments.rb

@@ -74,6 +74,7 @@ def create
         column I18n.t('active_admin.comments.resource'),      :resource
         column I18n.t('active_admin.comments.author'),        :author
         column I18n.t('active_admin.comments.body'),          :body
+        column I18n.t('active_admin.comments.created_at'),    :created_at
         actions
       end
     end