Add Nick change function
Add Nick change function

SeanThomasWilliams/go-ircevent,HenrySlawniak/go-ircevent,Elemental-IRCd/irc,iwanbk/ogric,phone/go-ircevent,pratikmallya/go-ircevent,DanielOaks/girc-go,dainis/go-ircevent,oniichaNj/go-ircevent,alaska/go-ircevent