Add tests as specified in #14

This PR adds tests for controller, route, model and component; the places t gets injected in so far.

Note that this PR also fixes a bug. T didn't get injected in model.
I would prefer to have this as a separate commit as it does not fit within the context of this PR.

In addition, we prefer the long-form for CPs:

```javascript
name: Ember.computed(function() {
   return this.t('name', 'John', 'Doe');
})
```