Ensure 1.3.0 features are on by default in master/canary.

The 1.3.0
[features.json](https://github.com/emberjs/ember.js/blob/v1.3.0-beta.2/features.json)
for reference.
Merge pull request #3890 from rjackson/ensure_beta_features_are_on_in_master

Ensure 1.3.0 features are on by default in master/canary.