Add YAML files to ignored list.
Add failing Order#new with no paremeters has no products test.
Make Order#new with no parameters should have 0 products pass.
Add failing Order#new with YAML file should have products test.
Make Order#new with YAML file should have products test pass.
Add Order#filter_by_category should filter products by category test.
Make Order#filter_by_category should filter products by category test pass.
Add Order#add should add a product and return it test.
Make Order#add_product should add a new product and return it test pass.
Add Order#filter_by_price should return products by a price range test.