We were very inconsistent regarding these rules.
Personally I prefer no empty lines around blocks, clases, etc... as
recommended by the Ruby style guide [1], and they're the default values
in rubocop, so those are the settings I'm applying.
The exception is the `private` access modifier, since we were leaving
empty lines around it most of the time. That's the default rubocop rule
as well. Personally I don't have a strong preference about this one.
[1] https://rubystyle.guide/#empty-lines-around-bodies
Using arrays made it difficult to order by more than one field (like the
`most_voted` scope does), and so we were ordering by `confidence_score`
and ignoring the `created_at` column.
Using an AR relation makes it easy to reuse the existing `most_voted`
scope.
This change has one side effect: now comments with equal votes are
ordered in descending order instead of having no specific order. That
means flaky specs which failed sometimes because they assumed comments
were ordered by date are now always green.
I've also re-added the `oldest` scope removed in 792b15b thinking it was
removed because using it with arrays was too hard.
