1.3.5

新增 UIViewController 两个便利方法设置导航栏状态

1. var nav_titleTextAttributes: [NSAttributedString.Key : Any]? ----> 设置导航栏的 Title text attributes. If the font or color are unspecified, appropriate defaults are supplied.
2. func nav_setBarBackgroundColor(color: UIColor) ----> 设置导航栏整体背景颜色,此方法同 nav_setBarTintColor, 命名语义上更直观