fix migration generator for AR 5.x (#463)

fixes #462, #444 and #466

Author: kirillseva

lib/generators/active_record/rolify_generator.rb

@@ -35,7 +35,7 @@ def inject_role_class
       end
 
       def copy_rolify_migration
-        migration_template "migration.rb", "db/migrate/rolify_create_#{table_name}.rb"
+        migration_template "migration.rb", "db/migrate/rolify_create_#{table_name}.rb", migration_version: migration_version
       end
 
       private
@@ -82,6 +82,16 @@ def prompt_missing_user
 MSG
       end
 
+      def rails5?
+        Rails.version.start_with? '5'
+      end
+
+      def migration_version
+        if rails5?
+          "[#{Rails::VERSION::MAJOR}.#{Rails::VERSION::MINOR}]"
+        end
+      end
+
     end
   end
 end

lib/generators/active_record/templates/migration.rb

@@ -1,4 +1,4 @@
-class RolifyCreate<%= table_name.camelize %> < ActiveRecord::Migration
+class RolifyCreate<%= table_name.camelize %> < ActiveRecord::Migration<%= migration_version %>
   def change
     create_table(:<%= table_name %>) do |t|
       t.string :name