Adds support for a Route Prefix, Improves Dockerfile

[ekristen]

• Adds support for a route prefix.

  • Allows nuts to run at a /path vs the root of a domain or subdomain.
  • Useful for if someone has one domain they want to use but multiple projects to support updates for and are using a reverse proxy.

• Improves the Dockerfile.

  • Switches to Official Node Image
  • Updates to Node 6 (small bump from 5)
  • Reorganized for better layer caching and less layer creation on subsequent builds.
  • Added dumb-init for proper signal handling/passing and zombie reaping.

[loprima-l]

Hi, I merged the project to a new repo to start maintain it, I would be glad if you can put your pull request here : https://github.com/loprima-l/nuts-2