Add failing property result test.

This test fails with expected { foo: 'bar' } to equal 'bar'.  The
property asserter in chai sets the object flag to the property value (in
the one argument form), but the promise adapting wrapper is not picking
up on this.
Rewrite with a new, simpler strategy.

Closes #14, #15, and #17, and probably more (which I will close by adding tests for them).