Add RSS button on footer

Author: rondy

_includes/bottom.html

@@ -8,7 +8,7 @@
     <div class="wrap">
       <div id="social">
         <ul>
-          <!-- <li class="menu-item"><a href="/" target="_blank"><img src="/images/social/RSS.png" /></a></li> -->
+          <li class="menu-item"><a href="/atom.xml" target="_blank"><img src="/images/social/RSS.png" /></a></li>
           <li class="menu-item"><a href="https://github.com/elixir-lang" target="_blank"><img src="/images/social/Github.png" /></a></li>
         </ul>
       </div>