title: Prevent React Route to re-run componentDidMount() on traversing back on same route
body: <p>For a given route <code>localhost:3000/my-link</code>, component <code>MyLink</code> is rendered.
  In <code>MyLink</code> component, ajax request is fired in <code>componentDidMount()</code> which then sets the <code>state</code> object of the <code>MyLink</code> class and renders the component.</p>
  
  <p>But when navigating to some other route and switching back to <code>/my-link</code> ajax is fired again. In short, whole state previously populated is lost. Can there be a way to check if the previous <code>state</code> is already populated, then prevent <code>componentDidMount</code> to be called?</p>