change compression level to 6, the default in nginx

this is a good blend of on the fly cpu utilization with file size
Thanks @jmervine

scripts/config/templates/nginx.conf.erb

@@ -9,7 +9,7 @@ events {
 
 http {
   gzip on;
-  gzip_comp_level 2;
+  gzip_comp_level 6;
   gzip_min_length 512;
   gzip_types text/plain text/css application/json application/x-javascript text/xml application/xml application/xml+rss text/javascript;
   gzip_vary on;