title: Changing segment content onPress
body: <p>I have segments and I want them to act as tabs. I tried using <code>react-navigation</code> <code>onPress</code> of each segment but it doesn't look nice.</p>
  
  <p>I want the segments to stay <strong>fixed</strong> at the top and on clicking each one  the <em>content should change</em> <strong>or</strong> <em>call a specific component</em> without reloading or noticing that the screen has changed.</p>
  
  <pre><code>&lt;Segment&gt;
    &lt;Button first&gt;
      &lt;Text&gt;Puppies&lt;/Text&gt;
     &lt;/Button&gt;
     &lt;Button&gt;
      &lt;Text&gt;Kittens&lt;/Text&gt;
      &lt;/Button&gt;
      &lt;Button last active&gt;
        &lt;Text&gt;Cubs&lt;/Text&gt;
      &lt;/Button&gt;
  &lt;/Segment&gt;
  &lt;Content&gt;
    &lt;Text&gt;Awesome segment&lt;/Text&gt;
  &lt;/Content&gt;
  </code></pre>