Fix dmail failures when akismet isn't configured.

config/danbooru_default_config.rb

@@ -619,6 +619,13 @@ module Danbooru
 
     def aws_sqs_cropper_url
     end
+
+    # Akismet API key. Used for Dmail spam detection. http://akismet.com/signup/
+    def rakismet_key
+    end
+
+    def rakismet_url
+    end
   end
 
   class EnvironmentConfiguration