Replace http link with https

This should fix the issue of "unsecure connection" warning in browsers.

Author: InfiniteCoder

docs/_themes/kr/layout.html

@@ -24,7 +24,7 @@
       © Copyright {{ copyright }}.
     </div>
     <a href="https://github.com/kushaldas/pym" class="github">
-        <img style="position: absolute; top: 0; right: 0; border: 0;" src="http://s3.amazonaws.com/github/ribbons/forkme_right_darkblue_121621.png" alt="Fork me on GitHub"  class="github"/>
+        <img style="position: absolute; top: 0; right: 0; border: 0;" src="https://s3.amazonaws.com/github/ribbons/forkme_right_darkblue_121621.png" alt="Fork me on GitHub"  class="github"/>
     </a>
 <script type="text/javascript">
   var _gauges = _gauges || [];