Add CocoaPods info to README
Add CocoaPods info to README

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