New cop: Empty line after conditions spanning multiple lines

[fatkodima]

Inspired by https://github.com/airbnb/ruby#multiline-if-newline

It is better to differentiate between conditions and body in this case

if @reservation_alteration.checkin == @reservation.start_date &&
   @reservation_alteration.checkout == (@reservation.start_date + @reservation.nights)

  redirect_to_alteration @reservation_alteration
end

rather than in this

if @reservation_alteration.checkin == @reservation.start_date &&
   @reservation_alteration.checkout == (@reservation.start_date + @reservation.nights)
  redirect_to_alteration @reservation_alteration
end

This can be extended to other syntax constructs like unless, while, etc.