Add all changes present in Iverson.

- `DS.EmbeddedRecordMixin` is totally customized. I will revert the changes
  and create an equivalent mixin inside Iverson.
- Just `normalizeRelationships` in the store needs to be updated to use
  `Typeable.detectDynamicType`

Our fork is based on the eb9743441f6b6df4f8d4733a211cc262dd1f339c commit
from Ember Data.