Delegate to DS._setupContainer when available to register service:store

[bmac]

This pr will automatically register the Store as a service for users running. Ember Data beta.16.

The one gotcha is if the user declares service:store in their needs. For Example:

moduleForComponent('actor-table', {
  // specify the other units that are required for this test
  needs: ['service:store']
});

The test will blow up with this error. Uncaught TypeError: Attempting to register an unknown factory: 'service:store', because this code https://github.com/switchfly/ember-test-helpers/blob/master/lib/ember-test-helpers/isolated-container.js#L81-L85 attempts to pull in a service:store from app/services/store.js which likely doesn't exist.