adhere to rubocop guidelines

db/migrate/20180504131648_create_users.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateUsers < ActiveRecord::Migration[5.0]
   def change
     create_table :users do |t|

db/migrate/20180504131705_create_rooms.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateRooms < ActiveRecord::Migration[5.0]
   def change
     create_table :rooms do |t|

db/seeds.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # This file should contain all the record creation needed to seed the database with its default values.
 # The data can then be loaded with the rails db:seed command (or created alongside the database with db:setup).
 #