add updated_at column to todos table

This timestamp was missing. All other tables with timestamps have update_at. Could use this in statistics

db/migrate/043_add_updated_at_to_todos.rb

@@ -0,0 +1,8 @@
+class AddUpdatedAtToTodos < ActiveRecord::Migration
+  def self.up
+      add_column :todos, :updated_at, :timestamp
+        end
+          def self.down
+              remove_column :todos, :updated_at
+                end
+                end