remove useless Gruntfile
remove useless Gruntfile

fengyapeng/muplayer,wangjun/muplayer,sdgdsffdsfff/muplayer,Denniskevin/muplayer,fengyapeng/muplayer,sdgdsffdsfff/muplayer,wangjun/muplayer,Baidu-Music-FE/muplayer,cnbin/muplayer,Denniskevin/muplayer,Baidu-Music-FE/muplayer,cnbin/muplayer