creates Manager

db/migrate/20150930082311_create_managers.rb

@@ -0,0 +1,12 @@
+class CreateManagers < ActiveRecord::Migration
+  def change
+    create_table :managers do |t|
+      t.string :username, null: false
+      t.string :password_digest, null: false
+      t.timestamp :last_login_at
+      t.timestamps
+    end
+
+    add_index :managers, [:username]
+  end
+end