Add some more structure to the Ruby files

[iHiD]

This does the following:

• Adds some extra structure by moving the stack, architecture, etc files into lib and adding a base file.
• Adds use of private and attr_accessor to make my life easier when writing tests for this.
• Also adds Rubocop and Prettier and the git hook in line with the other v3 repos.
• Fixes the non-building Dockerfile (Enjoy!!)
• Adds the exercism-config gem to the Gemfile. Bumping it here becomes the official way to bump it in the Dockerfile.

I think we should probably think about adding Groups to the Gemfile along with the other non-rails things.

@joshgoebel Any thoughts or can I merge this and we keep moving forward?

[iHiD]

Sweet. Thanks! :)