Ember apps can now be relative in any directory

In your Brocfile's EmberApp definition you would declare an alternate
root path:

```js
var app = new EmberApp({
  root: path.join(process.cwd(), 'tests/dummy')
});
```
Merge pull request #1338 from bcardarella/bc-relative-apps

Ember apps can now be relative in any directory
move qunit out of core and into an addon