Add and apply rubocop rules for empty lines

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

app/controllers/polls/questions_controller.rb

@@ -1,5 +1,4 @@
 class Polls::QuestionsController < ApplicationController
-
   load_and_authorize_resource :poll
   load_and_authorize_resource :question, class: "Poll::Question"
 
@@ -77,5 +76,4 @@ class Polls::QuestionsController < ApplicationController
         @answers = @question.question_answers.visibles
       end
     end
-
 end