Fix empty test, ensure that fields/associations can be supered to

This adds the logic for an empty test for models. The test was
intended to ensure that a field and association could be supered
to, but was accidentally left empty. This defines the test and
ensures it passes.
Merge pull request #56 from redding/jcr-fill-in-empty-test

Fix empty test, ensure that fields/associations can be supered to