put a sterner warning in nginx local.conf about not modifying it

conf/nginx-top.conf

 ## NOTE: This file is automatically generated by Mail-in-a-Box.
-##       Do not edit this file. It will be replaced each time
-##       Mail-in-a-Box needs to update the web configuration.
+##       Do not edit this file. It is continually updated by
+##       Mail-in-a-Box and your changes will be lost.
+##
+##       Mail-in-a-Box machines are not meant to be modified.
+##       If you modify any system configuration you are on
+##       your own --- please do not ask for help from us.
 
 upstream php-fpm {
 	server unix:/var/run/php5-fpm.sock;