title: adding max length attribute to ionic text field
body: <p>how do i set <strong>max length</strong> for ionic2 text field. I am able to set for '<strong>tel</strong>' field but not for <strong>text</strong> field.</p>
  
  <pre><code>&lt;ion-input maxlength="12" type="tel"&gt;
  </code></pre>
  
  <p>but the following one not working,</p>
  
  <pre><code>&lt;ion-input maxlength="12" type="text"&gt;
  </code></pre>