Repositories are a class of services to help with CRUD actions, most of
the functionality is reused across various Models. This creates a new
repository service that centralizes all this reused functionality.
Inheritance via ember `Service.extend` is used as opposed to
decorating via Mixins.
1. Move all repository services (and their tests) to a
services/repository folder
2. Standardize on a singular name format 'node vs nodes'
3. Create a new 'repository' service to centralize functionality. This
should be extended by 'repository' services
John Cowen