Add logic to bump Alpine in Node 8+ Node 8 started to use Alpine 3.6, so use that instead of the template 3.4 version
Add logic to bump Alpine in Node 8+
Node 8 started to use Alpine 3.6, so use that instead of the template 3.4 version

pesho/docker-node,nodejs/docker-node,joyent/docker-node,nodejs/docker-node,chorrell/docker-node,chorrell/docker-node