add DS.Errors object
Add API missing api docs for normalizeHash and keyForAttribute
Document the VERSION property
Merge pull request #1627 from bmac/doc-core

Document the VERSION property
Merge pull request #1626 from bmac/missing-serializer-docs

Add API missing api docs for normalizeHash and keyForAttribute
Merge pull request #1546 from tchak/ember-data-reboot-validation-errors

add DS.Errors object
Clean up the docs for DS.RESTAdapter
handle case of single object pushPayload
Merge pull request #1624 from bmac/rest-adapter-docs

Clean up the docs for DS.RESTAdapter
Merge pull request #1629 from tpitale/single-push-payload

Handle case of single object pushPayload
Allow async relationships changes and rollbacks.

* Proper relationship changes for async relationships.
* Proper rollback of relationships.
* Refactored DS.hasMany and DS.belongsTo.
* Added _relationship to DS.belongsTo (similar to _attributes in DS.attr).
* Allow didSetProperty to work with belongsTo relationships in model states.
* Fixed tests that were passing with old code but were not actually right.

Relationship changes now propagate correctly and model.rollback() works on
both belongsTo and hasMany relationships. Quite a few tests still need to
be written.