Use ember-dev test helpers.

* Move configuration, into `index.html`.  This is in preparation for
  publishing the test runner page to S3 (so users can hit
  `http://builds.emberjs.com/canary/ember-test.html`).
* Use updated helpers from ember-dev.
Merge pull request #9516 from rwjblue/use-test-helpers-from-ember-dev

Use ember-dev test helpers.