Rootless container image

[chevdor]

When security is a concern, better use rootless images.

I started working on the topic and I have a working rootless image.

You can see the diff here. This diff includes a bunch of other changes (See #77) that probably shouls be excluded from a PR.

Happy to propose a PR if this is welcome.

The fixes I made so far are:

• rootless image
• better ENV support
• option to not use supervisord
• much smaller image
• the image is built from the local source, and not from the github repo... which is also a better practise and allows building any tag/branch.

[cryptosharks131]

Yes, PRs are welcome!

[chevdor]

Here you go: #377