ruby with jemalloc based on debian-stretch
本镜像基于debian:stretch 制作，更换了ruby内存管理为jemalloc.此dockerfile 本地构建完成后直接push到 docker hub 上（astarup账号）.
git clone https://github.com/zhulux/debian-ruby-jemalloc.git
cd debian-ruby-jemalloc
docker build -t debian-stretch:ruby2.5.1打tag
docker tag debian-stretch:ruby2.5.1 astarup/debian-stretch:ruby2.5.1login and push to dockerhub
docker login
docker push astarup/debian-stretch:ruby2.5.1