fixing readme.txt versioning

Author: Pedro de Carvalho

readme.txt

@@ -4,7 +4,7 @@ Donate link: https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_i
 Tags: qtranslate, slug, multilanguage
 Requires at least: 3.3
 Tested up to: 4.1.0
-Version: 1.1.8
+Stable tag: 1.1.8
 License: GPLv2 or later
 License URI: http://www.gnu.org/licenses/gpl-2.0.html