Fix link to blog in nav

Author: fzaninotto

_includes/nav.html

@@ -17,7 +17,7 @@
                 <a href="{{ site.url }}/Demos.html">Demos</a>
             </li>
             <li>
-                <a href="https://marmelab.com/en/blog/#react-admin">Blog</a>
+                <a href="https://marmelab.com/blog/tags/react-admin">Blog</a>
             </li>
             <li>
                 <a