Remove config import from init to fix scaffold usage

[pjbull]

• Remove config import from __init__.py (not needed and also breaks since it is there in non-scaffold scenario)
• Refactor some repeated code
• Add import and import config tests
• Add changelog

Closes #370

[jayqi]

not needed

The main thing that happens in config right now that is valuable to auto-execute is this bit:

https://github.com/drivendataorg/cookiecutter-data-science/blob/bbfa1511ff724731ddd482bcffcd62fb1e6b1b83/%7B%7B%20cookiecutter.repo_name%20%7D%7D/%7B%7B%20cookiecutter.module_name%20%7D%7D/config.py#L24-L32

[pjbull]

The main thing that happens in config right now that is valuable to auto-execute is this bit:

Ah, that's a good point. Added back in.

[pjbull]

Just summarizing for my own understanding / posterity:

Nailed it! 🔨