change link for each category in sample side nav

Change-Id: I8e56114be1842bcca7f4373d80392090d2b51964
diff --git a/src/com/google/doclava/Doclava.java b/src/com/google/doclava/Doclava.java
index bc57fa2..e2388bd 100644
--- a/src/com/google/doclava/Doclava.java
+++ b/src/com/google/doclava/Doclava.java
@@ -1691,7 +1691,7 @@
     if (sortNavByGroups) {
       sampleGroupsRootNodes = new ArrayList<SampleCode.Node>();
       for (SampleCode gsc : sampleCodeGroups) {
-        String link = "samples/topic.html#t=" + gsc.mTitle.replaceAll(" ", "").trim();
+        String link =  "samples/" + gsc.mTitle.replaceAll(" ", "").trim().toLowerCase() + ".html";
         sampleGroupsRootNodes.add(new SampleCode.Node(gsc.mTitle, link, null, null, null,
             "groupholder"));
       }