Attachment spec - fix reference to fixture

Ensure we load from the gem's ./spec/fixtures/ folder instead of from
the dummy app's.
Fix FactoryGirl to work with the engine

* Make sure we load the factories from the gem instead of the dummy app.
* Our factories need to use the :class option to reference the
namespaced models.
Ignore bundle and dummy app
Fix Configurator specs use the right Configuration model name