Generate factory for unconventional relationships

[jasonmccreary]

With the merge of #154 there are many combinations of how a column may reference a model.

For example:

• owner_id: foreign:user
• foreign:countries.code

Currently there is a commented test which emphasizes the second example.

This issue to get this test to pass as well as add a test for first example which should generate a shorthand factory for the referenced model.

For example:

    // ...
    'owner_id` => factory(User::class),
    // ...