Use beforeEach in Factory#define description in prep for inheritance
Added test case for Factory#define inheritance, fails
Inheritance test case passes, needs error case
Added test case for undefined parent model in Factory#define, fails
All tests pass with inheritance added
Correct usage spec description, a model's key is not its name
Fix error message semantics wrt model key/name distinction
Merge pull request #5 from ranweiler/master

Allow inheritance from already-defined models in Factory.create