ember data v1.0.0-beta.9 release post

Don't merge quite yet.

cc @igorT @wycats @tomdale

reminder to self to add @kurko
Better support for nested records. 
BuildUrl now takes a record, on which you can look up the relationship if you need to build a nested url. For example 
```javascript
App.CommentAdapter = DS.RestAdapter.extend({
  buildUrl: function(type, id, record) {
    return "/posts/" + record.get('post.id') + "/comments/" + id;
  }
})
```

Added support for preloading records -> https://github.com/emberjs/data/blob/master/packages/ember-data/lib/system/store.js#L356