fix navigation back when site is not at the root url

Author: riccardomerlin

analysis-index.html

@@ -4,7 +4,7 @@
 
 <h1></h1>
 
-<a href="/index.html">&lt; back</a>
+<a href="../index.html">&lt; back</a>
 <ul>
     <li><a href="top10hotspots.txt">Top 10 hotspots</a></li>
     <li><a href="hotspots.html">Hotspots circular treemap</a></li>