Fix too verbose error logging on default production environment

issue was present on PHP < 5.4
diff --git a/index.php b/index.php
index cfb003e..e5f570e 100755
--- a/index.php
+++ b/index.php
@@ -61,7 +61,7 @@
 
 	case 'testing':
 	case 'production':
-		error_reporting(E_ALL ^ E_NOTICE ^ E_DEPRECATED ^ E_STRICT);
+		error_reporting(E_ALL & ~E_NOTICE & ~E_DEPRECATED & ~E_STRICT);
 		ini_set('display_errors', 0);
 	break;