title: yii2 - how to add new column with default value via schema
body: <p>how to add new column with default value via schema?
  I make as this:</p>
  
  <pre><code>$this-&gt;addColumn('users', 'email_notification', Schema::TYPE_SMALLINT . ' AFTER auth_key DEFAULT 0  ');
  </code></pre>
  
  <p>but it's not working.. </p>
  
  <p>Thanks</p>