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
There was a rare case we've found on some Travis builds where the system
time suddenly moved back to the past a couple of tenths of a second,
meaning `Time.current - resource.created_at` returned a negative number,
which lead to a division by zero.
