implement openID authentication

db/migrate/20140603092041_create_openids.rb

@@ -0,0 +1,12 @@
+class CreateOpenids< ActiveRecord::Migration
+  def change
+    create_table :openids do |t|
+      t.string :provider
+      t.string :email
+      t.string :uid
+      t.integer :user_id
+
+      t.timestamps
+    end
+  end
+end