Add failing test for resource without function passed not inheriting model from parent resource.

The recent enhancement (in 1.5.0.beta.x) for routes without `model` hooks to inherit their parent resources' model is great. However, does it make sense for this to apply to leaf resources as well?

A common use case for nesting resources without embedded leaf routes is for namespacing purposes. It seems like having such resources inherit the model from parent resources would not be expected, unless we are missing an obvious use case for this.

It may be okay to leave things as is but we just wanted to open the discussion as to whether this would be surprising or whether there should just be more clear documentation of the behaviour.

/cc @machty