created parts factory
created parts factory

explanation from:
http://hashrocket.com/blog/posts/test-driving-a-stubbed-api-in-ember-with-ember-cli-mirage

"Now QUnit yells because we have no links. Turn our list of cars into
links, so that when we click on one, we can see that car's parts."

omouse/ember-cli-mirage-tutorial,omouse/ember-cli-mirage-tutorial