adds swift to readme
adds swift to readme

imjerrybao/SIOSocket,MegaBits/SIOSocket,fjtrujy/SIOSocket,fjtrujy/SIOSocket,yonglehou/SIOSocket,emlynmu/SIOSocket,yonglehou/SIOSocket,sujianping/SIOSocket,emlynmu/SIOSocket,MegaBits/SIOSocket,imjerrybao/SIOSocket,sujianping/SIOSocket