启动hub主机：
java -jar selenium-server-standalone-2.39.0.jar -role hub
启动node
本地：java -jar selenium-server-standalone-2.39.0.jar -role node -port 5555
远程：java -jar selenium-server-standalone-2.39.0.jar -role node -port 5555 -hub http://hub主机ip/grid/register