fix(docker): base image node:8-alpine and upgrade to npm6 (#567) r=@jbuck,@vladikoff
fix(docker): base image node:8-alpine and upgrade to npm6 (#567) r=@jbuck,@vladikoff


mozilla/fxa-auth-server,mozilla/fxa-auth-server,mozilla/fxa-auth-server,mozilla/fxa-auth-server