title: Angular Material: md-tabs with no default selected tab
body: <p>Is there any way of defining tabs without a default active/selected tab?<br>
  If I use any value other than an integer, the first tab will always become active.</p>
  
  <p>There is an example in this <a href="http://codepen.io/marcossffilho/pen/xboayr" rel="nofollow">pen</a>:</p>
  
  <pre><code>angular
    .module('MyApp', ['ngMaterial'])
    .run(['$rootScope', function($rs) {
      $rs.selectedNegative = -1
      $rs.selectedUndefined = undefined
      $rs.selectedNull = null
      $rs.selectedString = 'none';
    }]);
  </code></pre>