emberjs/data — pull request #2061 by pixelhandler (2014-07-02 19:32:40+00:00)
Title: [Bugfix] embedded records mixin: key variable needed to be declared

- `key` was not declared prior to assignment in `serializeBelongsTo` method
- when embedded records using `serializeBelongsTo` use `keyForAttribute` not `keyForRelationship` like `serializeHasMany` does