Update alpine to version 3.5

On https://github.com/nodejs/docker-node/blob/master/4.7/alpine/Dockerfile, we are still using 3.4

Please let me know if something actually prevent you guys to switch to alpine:3.5 . I'm rebuilding all my containers using it :-p

Cheers!
Pascal | https://twitter.com/_pascalandy