Enable features given a 'go' status.

New features as of 2014/01/17:

* `ember-testing-routing-helpers`
* `ember-testing-triggerEvent-helper`
* `computed-read-only`
* `ember-metal-is-blank`
* `ember-eager-url-update`

Also, removed `composable-computed-properties` as it was accidentally
commited in another unrelated PR.
Merge pull request #4175 from rjackson/update_features-json

Enable features given a 'go' status.