iOS 分段Slider
调用方式如下：
SegmentSlider *slider = [[SegmentSlider alloc] initWithFrame:CGRectMake(20, 100, self.view.frame.size.width-40, 35)];
[self.view addSubview:slider];
slider.videoSegments = @[@0.2,@0.4,@0.7];
AudioSegment *a1 = [AudioSegment new];
a1.percentIn = 0.2;
a1.percentOut = 0.4;
slider.audioSegments = @[a1];
AudioSegment *a2 = [AudioSegment new];
a2.percentIn = 0.6;
a2.percentOut = 0.9;
slider.audioSegments = @[a1,a2];