Add missing links to FEATURES.md.
Add composable-computed-properties to FEATURES.md.
Add link to string-parameterize feature.
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