BDKNotifyHUDios指示器

BDKNotifyHUD 是一个用来显示临时的带边框的提醒信息，居中显示。

使用方法：

// Create the HUD object
BDKNotifyHUD *hud = [BDKNotifyHUD notifyHUDWithImage:[UIImage imageNamed:@"Checkmark.png"]
                                                text:@"This is a checkmark!"];
hud.center = CGPointMake(self.view.center.x, self.view.center.y - 20);

// Animate it, then get rid of it. These settings last 1 second, takes a half-second fade.
[self.view addSubview:hud];
[hud presentWithDuration:1.0f speed:0.5f inView:self.view completion:^{
    [hud removeFromSuperview];
}];