Update broccoli-sass to support sass files
Merge pull request #1367 from jakecraige/sass-support

Update broccoli-sass to support sass files
EmberAddon

Will call the EmberApp constructor with defaults for addon projects. In
the addons Brocfile only the following is required:

```js
var EmberAddon = require('ember-cli/lib/broccoli/ember-addon');
var addon = new EmberAddon();
module.exports = addon.toTree();
```