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.
* Fix assertion counts (now that we are using `QUnit.testStart` and
* `QUnit.testDone` any assertions made in them do not count towards the
  total `expect` count).