adds devise's confirmable/reconfirmable to user

db/migrate/20150731110702_add_confirmable_to_devise_for_users.rb

@@ -0,0 +1,13 @@
+class AddConfirmableToDeviseForUsers < ActiveRecord::Migration
+  def change
+    # Confirmable
+    add_column :users, :confirmation_token, :string
+    add_column :users, :confirmed_at, :datetime
+    add_column :users, :confirmation_sent_at, :datetime
+
+    # Reconfirmable
+    add_column :users, :unconfirmed_email, :string
+
+    add_index :users, :confirmation_token, unique: true
+  end
+end