Dans spec work

A redo of spec_work. This pull request redoes the overall directory structure, keeping the nomenclature of DDD but also making testing easier as the specs are now in parallel. I moved the integration specs into spec/integration/* and made placeholder unit tests under spec/domain/*

Two unit tests are fully fleshed out: cargo_spec.rb and delivery_spec.rb. They should hopefully be good examples for future unit tests... as well as discussion poitns.

Please feel free to reject the pull request for 'spec_work'