Enable seq to be imported from baker

[radwon]

Enable the seq() function to be imported from the baker module like
it is in the recipe module so that it can be used as baker.seq() if
preferred or to avoid namespace issues.

The current import can be left in place for backwards compatibility
or to continue importing seq as before.

Closes #75

[amureki]

Thanks for a good proposal @radwon !

I am wondering if we should consider following the same pattern for other things that we often import, for example stuff from recipe module - recipe.Recipe, recipe.foreign_key etc.

Then maybe we can think about better unifying the whole thing maybe, otherwise we'd have too many possibilities (which is not always a good practice):

from model_bakery import baker, recipe

baker.seq("test")
recipe.seq("test")
baker.Recipe("mymodel")
recipe.Recipe("mymodel")

Anyways, I'd love to hear other opinions here before going forward.
@radwon @anapaulagomes @berinhard what do you think?

[anapaulagomes]

Sounds good to me, @amureki. @radwon, thank you for your contribution! 🎉

[berinhard]

I agree with your suggestion @amureki for the Recipe as well! Can you document it on a new issue?

[berinhard]

@radwon this PR looks great! Can I ask you just for 2 minor things?

1. Add a simple unit test to ensure the baker.seq is working as expected. Maybe a test very similar to this one;
2. Update the CHANGELOG.md file with this addition;

And thanks for being careful on updating the docs as well =)

[radwon]

@berinhard I've made the requested changes, and also made some changes to test_recipes.py renaming self.fail to pytest.fail as the TestDefiningRecipes class doesn't actually have a fail method.

Hope that's OK. Let me know if there's anything else.

[berinhard]

Thanks @radwon! It looks great =)

[berinhard]

I'm merging since @anapaulagomes had already approved this previously and @radwon only added tests to make sure the changes he'd introduced are working.