Merge pull request cocos2d#3178 from xiaofeng11/develop

update version number, prepare release version

Author: pandamicro

cocos2d/core/platform/CCConfig.js

@@ -31,7 +31,7 @@
  * @type {String}
  * @name cc.ENGINE_VERSION
  */
-window["CocosEngine"] = cc.ENGINE_VERSION = "Cocos2d-JS v3.9 Beta";
+window["CocosEngine"] = cc.ENGINE_VERSION = "Cocos2d-JS v3.9";
 
 /**
  * <p>