remove syncForTest
Failing test: DS.Model.save() causes an inconsistent attribute changes
Throw a useful error when deserializing an embedded relationship
Fix changedAttributes when saves are rejected

Also move _attributes and _inFlightAttributes to Object.create(null)
make the Object.create assertion more specific
Merge pull request #2511 from emberjs/more-ie8-oo-create-fixes

make the Object.create assertion more specific
Add Test Coverage for `ember-data/transforms`

Transforms are not tested at the `unit` level. Adding tests at the
`unit` granularity allows for regression testing if the
implementation covered by the `acceptance` level tests should change.
Merge pull request #2509 from seanpdoyle/add-tests-number-transform

Add Test Coverage for `DS.NumberTransform`
changelog/ember add-on update; release beta.12
Add an example to the store.fetch docs
Merge pull request #2514 from bmac/fetch-example

Add an example to the store.fetch docs
post-release version bump to beta.13.canary
Merge branch 'master' of github.com:emberjs/data
Added test for model.changedAttributes()
command was correct but text not
Merge pull request #2521 from kellyselden/fix-readme-ember-cli

command was correct but text not
Merge pull request #2518 from wecc/model-changed-attributes-test

Added test for model.changedAttributes()
[BUG] Transform `{NaN,Infitity,-Infinity}` to null

https://github.com/emberjs/data/pull/2509#discussion_r20898264

Serializing and Deserializing invalid numeric `JSON` (`NaN`,
`Infinity`, `-Infinity`) should result in `null`.
A hasMany updated link should not remove new children
add test for no attribute type

from http://emberjs.com/guides/models/defining-models/:
"If you don't specify the type of the attribute, it will be whatever was
provided by the server. You can make sure that an attribute is always
coerced into a particular type by passing a type to attr:"