Removes commenter poro, updates post poro to include snakecase attrs

This commit removes the commenter poro and updates the post poro to
include snakecase attrs (created_at and updated_at) to test converting
keys to various formats such as camelizing.
Updates tests to use Post poro vs. Commenter

This commit updates the tests to use the Post poro rather than
introducing a new Commenter poro.