ESTabBarController 设置之后，默认没有itme高亮

[mzx-699]

• 设置了两个，但是没有一个高亮

func addChildViewController() {
    addChildViewController(vc: OverallViewController(), title: "天气预报", imageName: "weather")
    addChildViewController(vc: WeatherDetailViewController(), title: "当日情况", imageName: "detail")
    
    
}

func addChildViewController(vc: UIViewController, title: String, imageName: String) {
    //设置标题---由内至外设置的
    //设置图像
    //导航控制器
    vc.tabBarItem = ESTabBarItem(ESBouncesContentView(), title: title, image: UIImage(named: imageName), selectedImage: UIImage(named: imageName + "_sel"))
    let nav = ESNavigationController(rootViewController: vc)
    self.addChild(nav)
}