Add debugging aid.

nginx.conf

@@ -14,6 +14,10 @@ http {
 
     access_log nginx/access_log;
 
+    # To debug the rewrite rules, enable these directives:
+    #error_log stderr notice;
+    #rewrite_log on;
+
     include /etc/nginx/mime.types;
     default_type application/octet-stream;