Don't open custom menus in a new tab (#27)

layouts/partials/navbar.html

@@ -44,7 +44,7 @@
         {{ end }}
         {{ range site.Params.customMenus }}
           <li class="nav-item">
-            <a class="nav-link" href="{{ .url }}" target="/">{{ .name }}</a>
+            <a class="nav-link" href="{{ .url }}">{{ .name }}</a>
           </li>
         {{ end }}
       </ul>