switch base image from alpine-shellcheck to alpine-node:7 because of selenium v3 require node v6.9
switch base image from alpine-shellcheck to alpine-node:7 because of selenium v3 require node v6.9

wechaty/wechaty,binsee/wechaty,binsee/wechaty,Chatie/wechaty,mukaiu/wechaty,Chatie/wechaty,Chatie/wechaty,wechaty/wechaty,mukaiu/wechaty,mukaiu/wechaty,binsee/wechaty,zixia/wechaty,zixia/wechaty,wechaty/wechaty,lijiarui/wechaty,lijiarui/wechaty