Add Ember Data 1.0.0-beta.8.

The files are from the [beta builds page](http://emberjs.com/builds/#/beta):
[beta/ember-data.prod.js](http://builds.emberjs.com/beta/ember-data.prod.js)
[beta/ember-data.min.js](http://builds.emberjs.com/beta/ember-data.min.js)
[beta/ember-data.js](http://builds.emberjs.com/beta/ember-data.js)