Fix http sidebar link

Author: dbader

docs/_templates/sidebarintro.html

@@ -56,9 +56,9 @@ <h3>Contributors</h3>
 
 <h3>Useful Links</h3>
 <ul>
-  <li><a href="http://python-guide.org/">The Guide Website</a></li>
-  <li><a href="http://github.com/kennethreitz/python-guide">The Guide @ GitHub</a></li>
-  <li><a href="http://github.com/kennethreitz/python-guide/issues">Issue Tracker</a></li>
+  <li><a href="https://docs.python-guide.org/">The Guide Website</a></li>
+  <li><a href="http://github.com/realpython/python-guide">The Guide @ GitHub</a></li>
+  <li><a href="http://github.com/realpython/python-guide/issues">Issue Tracker</a></li>
   <li><a href="https://media.readthedocs.org/pdf/python-guide/latest/python-guide.pdf">The Guide as a PDF</a></li>
 </ul>