iOS 8：CAKeyframeAnimation实现界面晃动动画

QQ空间在输错帐号或密码时会一左一右晃动，这种动画可使用关键帧动画实现。

- (void)shakeView:(UIView *)view {
    CAKeyframeAnimation *shakeAnimation = [CAKeyframeAnimation animation];
    shakeAnimation.keyPath = @"transform.translation.x";
    CGFloat margin = 10;
    shakeAnimation.values = @[@(0), @(-margin), @(margin), @(0)];
    shakeAnimation.duration = 0.125;
    shakeAnimation.repeatCount = 2;
    [view.layer addAnimation:shakeAnimation forKey:nil];
}