title: How to dismiss keyboard for UITextView with return key?
body: <p>In IB's library, the introduction tells us that when the <kbd>return</kbd> key is pressed, the keyboard for <code>UITextView</code> will disappear. But actually the <kbd>return</kbd> key can only act as '\n'. </p>
  
  <p>I can add a button and use <code>[txtView resignFirstResponder]</code> to hide the keyboard. </p>
  
  <p>But is there a way to add the action for the <kbd>return</kbd> key in keyboard so that I needn't add <code>UIButton</code>?</p>