title: yii2: how to creating a back link button
body: <p>I'm new in Yii2 and I'm not able to find something to do a back button in Yii2,
  I found the solution in Yii1 is:</p>
  
  <pre><code>echo CHtml::link('Back',Yii::app()-&gt;request-&gt;urlReferrer);
  </code></pre>
  
  <p>but I'm not able to find a solution in Yii2,
  can you help me?</p>