improve performance of Ember.guidFor and Ember.generateGuide on
Ember.Objects

Ember's guidKey uses defineProperty so that it is not enumerable,
this is a great idea, but can cost be a hard hit. Luckily though,
we pre-shape all ember objects to have a GUID_KEY slot. Unfortunately,
in guidFor and generateGuid we redefine the property. Not only is this
wasteful, but Object.defineProperty is incredibly costly.
Merge pull request #4158 from stefanpenner/improve-performance-of-guid-for

improve performance of Ember.guidFor and Ember.generateGuide on
Update ember-dev, use the new async expectDeprecation helper
Merge pull request #4166 from mixonic/async-deprecate

Use the new async expectDeprecation helper
[FEATURE ember-views-bindable-attributes]

Any properties listed in `bindableAttributes` that exist on the
`Ember.View` at the time of the first render will be bound (and
observed). However, any properties that do not exist on the View
instance will not have observers setup.

The main difference here from `attributeBindings` is the fact that the
observers are only setup when needed.