16 -- 设置导航栏字体

//设置导航栏背景颜色
    self.navigationController?.navigationBar.barTintColor =UIColor.redColor()
    
    let dict:NSDictionary = [NSForegroundColorAttributeName:UIColor.blackColor(),NSFontAttributeName : UIFont.boldSystemFontOfSize(18)]
    //标题颜色
    self.navigationController?.navigationBar.titleTextAttributes = dictas? [String : AnyObject]
    //item颜色
    self.navigationController?.navigationBar.tintColor =UIColor.grayColor()