Initial work on order classes and tests.
Adding user address model, list and test classes.
Working on order model and tests.
Adding test case for updating a user's address.
Updating docs.
Adding test assertions for the order list model.
Adding order status models and test class.
Adding ability to fetch items and address details for an order and tests for this.
Order getItems() method now returns an array of order item objects.
Fixing address models.
Merge branch 'master' into order_apis
Changing method definition to match the parent class.
Adding order note model and test case in order test class.
Adding support for saving and loading order notes and shipments.
Updating docs.