Generalize documentation helpers

Change-Id: Iaba69a433f25d2160857694b0b434c51c02c0367
diff --git a/templates/doc/korap/karang.html.ep b/templates/doc/korap/karang.html.ep
index 5c60d48..820a12b 100644
--- a/templates/doc/korap/karang.html.ep
+++ b/templates/doc/korap/karang.html.ep
@@ -1,6 +1,6 @@
 % layout 'main', title => 'KorAP: Karang';
 
-<h2 id="tutorial-top">Karang</h2>
+%= page_title
 
 %= korap_overview 'karang'