Feature/card deck api

This PR lays the groundwork for calling the backend API from JS and in particular from model objects. Two configuration options are passed to the API object through requirejs's config option:

- **apiRoot**: This is the location of the root endpoint of the API (i.e. /api)
- **apiKey**: This is the key needed to access the API.

An API key is not required yet, since we don't really have much of an API, but I anticipate that we will once this is properly built out. For now, the **apiKey** is ignored, but we can easily modify the API object to include it in all requests. The **apiRoot** is necessary because this path may vary depending on the host configuration (i.e. shared hosting) and versioning (instead of /api, it might be /api/v2 in the future). We want to avoid hard-coding API urls in `$.ajax()` calls, so by calling `API.ajax()`, we only need to pass a relative path and can augment or modify the requests in the future.

@jazahn Can you review this?