Add and apply EmptyLineAfterGuardClause rule

We were inconsistent on this one. I consider it particularly useful when
a method starts with a `return` statement.

In other cases, we probably shouldn't have a guard rule in the middle of
a method in any case, but that's a different refactoring.

app/models/poll/question.rb

@@ -63,6 +63,7 @@ class Poll::Question < ApplicationRecord
 
   def self.answerable_by(user)
     return none if user.nil? || user.unverified?
+
     where(poll_id: Poll.answerable_by(user).pluck(:id))
   end
 

app/models/poll/question/answer/video.rb

@@ -11,6 +11,7 @@ class Poll::Question::Answer::Video < ApplicationRecord
     return if url.blank?
     return if url.match(VIMEO_REGEX)
     return if url.match(YOUTUBE_REGEX)
+
     errors.add(:url, :invalid)
   end
 end

app/models/poll/recount.rb

@@ -21,6 +21,7 @@ class Poll::Recount < ApplicationRecord
 
     [:white, :null, :total].each do |amount|
       next unless send("#{amount}_amount_changed?") && send("#{amount}_amount_was").present?
+
       self["#{amount}_amount_log"] += ":#{send("#{amount}_amount_was")}"
       amounts_changed = true
     end