Document cookbook_artifact API endpoints

[clintoncwolfe]

Describe the problem

Write documentation on the https://github.com/chef/chef-web-docs/blob/master/content/api_chef_server.md page for the /organization/*/cookbook_artifacts/* endpoints.

Here is one place where the API is tested revealing some of its structures.

Here is the implementation of the cookbook_artifacts/NAME/ID handler.

Related: #19 and #21 implement the API in this library.

Acceptance Criteria

1. The Chef Server API documentation contains documentation for for the endpoints cookbook_artifacts, cookbook_artifacts/NAME, and cookbook_artifacts/NAME/ID for the GET verb.
2. The endpoints are documented for the DELETE, and PUT verbs as applicable.

[tyler-ball]

Merged!