Root element auto-add ordering

In situations where the the `#ember-testing` root element is not already in the testing document *and the first test uses `moduleForComponent`*, tests fail with the error:

```
Setup failed on root element is auto-added before moduleFor callback: Assertion Failed: Unable to add "ember-application" class to rootElement. Make sure you set rootElement to the body or an element in the body.
```

This is because the callback that `moduleForComponent` provides to `moduleFor` expects the root element to exist already ([by calling `setup` on an event dispatcher](https://github.com/rwjblue/ember-qunit/blob/efdc1232341990c92486f686d01dfb350e925896/lib/module-for-component.js#L19)).

This also fixes a failing deprecation test because of newer deprecations in 1.7.0.