Clean up cookbook, prep for larger refactoring

Some fixes/clean up, and prep for larger refactoring:

* Give the cookbook a name for use with Berkshelf
* Ensure consistency of code style, adhering to the [Ruby Style Guide](https://github.com/bbatsov/ruby-style-guide), using [RuboCop](https://github.com/bbatsov/rubocop)
* Consistently use attributes for determining paths for Archiva files
* Use the `apt` cookbook to set up slightly out-of-date Debian-style systems properly for package installation
* Ignore some files properly (prep for uploading cookbook to Supermarket)
* Refactor the `nginx_proxy` recipe to work by including the `default` recipe
    - This is necessary because notifying a service that isn’t either defined in a recipe, or included from another one, prevents testing & is generally not solid pattern to follow (need your dependencies!)