Add best-practice features

[jamierajewski]

This repo contains some simple best-practices for building Docker containers, primarily focused around security but also stability.

• Since I have a custom entrypoint already, add --init option to all run commands in the docs which will use tini
• Add nonroot user as specified
• No need for bind-tools, and not using alpine linux

The nonroot user creation may require slightly modified commands since this container is CentOS-based while that one is Alpine-based.