Fix mode menu 'approve' option.

* Fix routing error in respond_with (didn't use /moderator namespace).

* Fix /moderator/posts/approvals.json response to return full
  PostApproval object, not just a success/failure message.

* Simplify the javascript a bit (use $.post instead of $.ajax).

app/controllers/moderator/post/approvals_controller.rb

@@ -9,7 +9,7 @@ module Moderator
         cookies.permanent[:moderated] = Time.now.to_i
         post = ::Post.find(params[:post_id])
         @approval = post.approve!
-        respond_with(@approval)
+        respond_with(:moderator, @approval)
       end
     end
   end