title: md-char-count not updating in md-input-container
body: <p>Consider the following simple md-input-container with textarea inside:</p>
  
  <pre><code>&lt;md-input-container class="md-block"&gt;
      &lt;textarea aria-label="tt" ng-model="obj.prop" md-maxlength="250" rows="5"&gt;&lt;/textarea&gt;
  &lt;/md-input-container&gt;
  </code></pre>
  
  <p>When i update <code>obj.prop</code> in my controller, the text is changed (therefore i should call <code>$scope.$evalAsync()</code> too). However, the <code>md-char-count</code> is still not updated. In order it to be updated, user will click on text-area and change it. Only then it is being changed.</p>
  
  <p>I think its a <a href="https://github.com/angular/material/issues/1983" rel="nofollow">known bug</a> but is there any improvements or is there a -at least- a workaround to this problem?</p>
  
  <p>Here you find <a href="http://codepen.io/anon/pen/adxJgX?editors=1111" rel="nofollow">a codepen</a></p>
  
  <p><em>ps(if needed):angular-material version 1.0.1 &amp; angular 1.4.5</em></p>