Return instancetype rather than id
Return instancetype rather than id

jianyelijun/ASValueTrackingSlider,alskipp/ASValueTrackingSlider,hejunbinlan/ASValueTrackingSlider,ezescaruli/ASValueTrackingSlider,vantientu1703/ASValueTrackingSlider,vince4/ASValueTrackingSlider,3squared/ASValueTrackingSlider,elegion/ios-pods-ASValueTrackingSlider,puvanarajan/ASValueTrackingSlider,shenyuan000/ASValueTrackingSlider