I added this check because otherwise the proxy server is always used and there is no way to turn this off.

The behavior of explicitly setting the method to `proxy` would expected, as described [here](https://github.com/stefanpenner/ember-app-kit/commit/3bed5f808f9a58d46bd4eee2dd10b64380ba5bb9#diff-b30dfc2524ff096070449e571248452bR17).