chore: cherry-pick from #100

[justlevine]

What

This PR cherry-picks the general cleanup changes from #100

Specifically:

• Some CI config files ( .gitattributes, codeception.dist.yml) have been cleaned up.
• Autoloader class has been refactored for DRYness.

Why

How

Testing Instructions

Additional Info

Checklist:

• [x] My code is tested to the best of my abilities.
• [x] My code follows the WordPress Coding Standards.
• [x] My code has proper inline documentation.
• [x] I have added unit tests to verify the code works as intended.
• [x] I included the relevant changes in CHANGELOG.md

[coveralls]

coverage: 82.571% (+0.1%) from 82.459% when pulling 3177a2572382fa23f8a5dd3c274c8d70c33a0ea6 on justlevine:chore/cleanup into 6f97d2b6ce185f15cfa91638155346b204e1077a on AxeWP:develop.