Fix nodejs version regression in Docker
Fix nodejs version regression in Docker

Switch to ruby:2.4-stretch to ensure nodejs 4.8.2 is installed.

iridakos/duckrails:release-v2.1.3 nodejs --version => v4.8.2
iridakos/duckrails:release-v2.1.4 nodejs --version => v0.10.29

iridakos/duckrails,iridakos/duckrails,iridakos/duckrails,iridakos/duckrails