Create 6 queries
Update postgres open method and refactored queries
Add query to get the 5 posts with the longest-running comment threads
Create new query

* Get all posts by a specific user that have comments,
* but which that user hasn't commented on.
Create new query

* Finds category of post each user has made the most comments on.
Update query to:

* Get the 5 most-commented-on posts that were created in the last 7 days