cocos2dx将背景色改为白色

1.更改场景类的继承关系。将HelloWorld : public class cocos2d::CCLayer 更改为HellowWorld : public class cocos2d::CCLayerColor.

2.更改初始化函数。将CC_BREAK_IF(! CCLayer::init())更改为 CC_BREAK_IF(!CCLayerColor::initWithColor(ccc4(255,255,255,255)));