Add twitter follow button

Author: debugger22

app/index.html

@@ -94,6 +94,7 @@ <h4>About</h4>
         <div>icons made by <a href="http://www.flaticon.com/authors/freepik" target="_blank" title="Freepik">Freepik</a></div>
       </div>
       <div class="social-buttons">
+        <a class="twitter-follow-button" data-show-count="false" data-show-screen-name="false" data-size="small" href="https://twitter.com/GithubAudio">Follow</a><br/>
         <a href="https://twitter.com/share" class="twitter-share-button" data-show-count="false" data-text="Listen to music generated by events happening across GitHub. #github #music">Tweet</a><script async src="//platform.twitter.com/widgets.js" charset="utf-8"></script><br/>
         <div class="fb-share-button" data-href="https://github.audio" data-layout="button" data-size="small" data-mobile-iframe="true"><a class="fb-xfbml-parse-ignore" target="_blank" href="https://www.facebook.com/sharer/sharer.php?u=https%3A%2F%2Fgithub.audio%2F&amp;src=sdkpreparse">Share</a></div>
       </div>