Fix layoutSubviews error that occurs when using AutoLayout and subclassing NMRangeSlider
Fix layoutSubviews error that occurs when using AutoLayout and subclassing NMRangeSlider

jfradj/NMRangeSlider,jiamaozheng/NMRangeSlider,Sega-Zero/NMRangeSlider,neonaldo/NMRangeSlider,muZZkat/NMRangeSlider,ivasic/NMRangeSlider,mvelikov/NMRangeSlider,namanhams/NMRangeSlider