title: React Fabric UI Pivot unmounts component on PivotItem change
body: <p>I'm using a Pivot component from FabricUI but I'm stuck because I have several PivotItems and every PivotItem has a child component that talks to the server when it's mounted. Every time I change a pivot item, current component get's unmounted and a new one is mounted. </p>
  
  <pre><code>&lt;Pivot&gt;
      &lt;PivotItem linkText='One' itemKey='0'&gt;
         &lt;GridDataOne/&gt;  
      &lt;/PivotItem&gt;
  
      &lt;PivotItem linkText='Two' itemKey='1'&gt;
          &lt;GridDataTwo/&gt;  
      &lt;/PivotItem&gt;
  &lt;/Pivot&gt;
  
  class GridDataTwo extends React.Component&lt;any,any&gt; {
     ...
     componentDidMount() {
         fetchDataFromServer()...
     }
  }
  </code></pre>
  
  <p>How can I avoid this kind of behaviour? Is it possible to hide unactive pivot items rather then unmounting it?</p>