query lookup creating more objects than it should
Adds RecipeForeignKey class so model_mommy's recipe can differs a common
callable method from another recipe being used as a foreign key on recipe
creation.
Refactors filter_fk_attrs signature to receive the field name instead of the
field object to make it more reusable.
Makes foreign key field lookup to work with model_mommy recipes
Refactors the tests by splitting the make method's scenario from the prepare
method's scenario.