Update README.mdown
Update README.mdown

Noted that UIView-based version is available on different branch.
cbpowell/MarqueeLabel,KBvsMJ/MarqueeLabel,litt1e-p/MarqueeLabel,cbpowell/MarqueeLabel,ByunghooLim/MarqueeLabel,RacZo/MarqueeLabel,ihello/MarqueeLabel,suchitabohra/MarqueeLabel,Anish-kumar-dev/MarqueeLabel,amitmalhotra/MarqueeLabel,yunzhongyoulong/MarqueeLabel,zmcadam/MarqueeLabel