Merge pull request phaserjs#3344 from samme/fix/util-string-format

Fix Phaser.Utils.String.Format

Author: photonstorm

src/utils/string/Format.js

@@ -20,12 +20,10 @@
  */
 var Format = function (string, values)
 {
-    string.replace(/%([0-9]+)/g, function (s, n)
+    return string.replace(/%([0-9]+)/g, function (s, n)
     {
         return values[Number(n) - 1];
     });
-
-    return string;
 };
 
 module.exports = Format;