- Fixing this.attributes undefined if validation fails.
- Same validation skipping condition for the constructor as in Backbone.Model.prototype._validate.
- Fixing a test.
Merge branch 'high_performance_collection_set_and_model_constructor'

* high_performance_collection_set_and_model_constructor:
  - Fixing this.attributes undefined if validation fails. - Same validation skipping condition for the constructor as in Backbone.Model.prototype._validate. - Fixing a test.