If a post doesn't have a featured image, the app first checks for a "featured_media" object, and if that doesn't exist it then searches the content looking for a suitably large image.

There are a few bugs with this right now, though:

1. If "featured_media" exists but is empty, the app skips searching for a large image
2. If app only searches WP posts for large images (so RSS posts coming from a WP blog are skipped)
3. When post detail shows the featured image above the post, it crops it unnecessarily
4. Featured image is sometimes incorrectly changed when post is updated by detail view