CartCtrl: Connect to api.azurestandard.com

This mostly works now, although we're still missing a few attributes
in the API:

* Estimated drop-trip delivery dates
* order_line.volume, or order_line.product.volume.
* order.shipping, and possibly order.tax.  Or a more generic
  order.auxiliary object with name keys and dollar values.
* A displayPrice filter for pretty-printing price structures (two
  decimal places, per-pound, discounts...).

I'm also just selecting the first cart as the main order, and haven't
added a UI for switching between carts.  The goal there will be to
have the next-to-cutoff cart be the default cart, and to have a
dropdown menu that the user can use to select an alternative cart.
We'll store the alternative choice in Angular's $scope (or
$rootScope?), since Benjamin doesn't want it to persist between
refreshes.  I'd consider having it persist between refreshes, but be
bound to the current session, but then we'd need more API endpoints to
set that for the session.