Update mailing list link on homepage

Author: mattcone

index.html

@@ -57,7 +57,7 @@ <h4 class="no-anchor">Take it up a notch.</h4>
         <h2 class="no-anchor">Stay in the loop.</h2>
         <p class="lead">Sign up now to get priority notifications about <em>The Markdown Guide</em>.</p>
         <br/>
-        <a class="btn btn-default btn-lg" href="https://mailchi.mp/83d1d4363848/signup" style="margin-top: -10px">Stay Updated</a>
+        <a class="btn btn-default btn-lg" href="https://pika.forklabs.com/subscription/form" style="margin-top: -10px">Stay Updated</a>
       </div>
     </div>
     {% include footer.html %}