Enable some Rails cops

lib/tasks/2017_07_26_clean_birthdate_on_individual.rake

@@ -19,7 +19,7 @@ namespace :'2017_07_26_clean_birthdate_on_individual' do
       puts "cleaning #{i.birthdate}"
       new_date = Date.strptime(i.birthdate, "%d/%m/%y")
       if new_date.year > 2017
-        new_date = new_date - 100.year
+        new_date = new_date - 100.years
       end
       i.update(birthdate: new_date.iso8601)
     end

lib/tasks/2017_10_30_copy_commentaire_piece_justificative_to_file.rake

@@ -41,7 +41,7 @@ namespace :'2017_10_30_copy_commentaire_piece_justificative_to_file' do
       end
 
       commentaire.save
-      if !commentaire.file.present?
+      if commentaire.file.blank?
         puts "Failed to save file for commentaire #{commentaire.id}"
       end
     end

lib/tasks/cloud_storage.rake

@@ -105,7 +105,7 @@ namespace :cloudstorage do
 
     @cont.objects_detail.each { |object, details|
       last_modified = DateTime.parse(details[:last_modified])
-      @cont.delete_object(object) if last_modified.utc <= (Time.now - 2.year).utc
+      @cont.delete_object(object) if last_modified.utc <= (Time.now - 2.years).utc
     }
   end
 end