add support for gzip_disable

nginx/templates/config.jinja

@@ -39,6 +39,7 @@ http {
     gzip_buffers {{ nginx.get('gzip_buffers', '16 8k') }};
     gzip_http_version {{ nginx.get('gzip_http_version', '1.1') }};
     gzip_types {{ nginx.get('gzip_types', ['text/plain', 'text/css', 'application/json', 'application/x-javascript', 'text/xml', 'application/xml', 'application/xml+rss', 'text/javascript'])|join(' ') }};
+    gzip_disable "{{ nginx.get('gzip_disable', 'msie6' }}";
 
     # turn on nginx_status on localhost
     server {