Resolve "Refactor publication system"

Closes #25 (closed)

Maybe consider the following requirements:

• Make is_published selected via a checkbox (selected/not selected) instead of radio button (yes/no)
• Make a button that uses route /posts/{uuid}/publish to publish a post
• Make a button that uses route /posts/{uuid}/unpublish to unpublish a post
• On forms, maybe consider using conditionals on whether showing publish or unpublish posts, but not both