Fix buildURL to match ember-data signature.
Fix buildURL to match ember-data signature.

This was missing the snapshot argument, which could screw up anyone
overriding buildUrl.

mike-north/ember-api-actions,mike-north/ember-api-actions,truenorth/ember-api-actions,mike-north/ember-api-actions,mike-north/ember-api-actions,truenorth/ember-api-actions