Prepare release 2.8

Change-Id: I98c36a7763387cd27df88713e68035dff222b187
diff --git a/docs/source/_templates/indexcontent.html b/docs/source/_templates/indexcontent.html
index 71289dd..c5810a1 100644
--- a/docs/source/_templates/indexcontent.html
+++ b/docs/source/_templates/indexcontent.html
@@ -59,8 +59,9 @@
       <td width="50%" valign="top">
         <h2>ndnSIM Versions</h2>
         <div class="tile">
-          <p class="biglink"><a class="biglink" href="#">ndnSIM 2.7</a><br/>
-            <span class="linkdescr">latest version</span></p>
+          <p class="biglink"><a class="biglink" href="#">ndnSIM 2.8</a><br/>
+              <span class="linkdescr">the latest version</span></p>
+          <p class="biglink"><a class="biglink" href="https://ndnsim.net/2.7/">ndnSIM 2.7</a><br/>
           <p class="biglink"><a class="biglink" href="https://ndnsim.net/2.6/">ndnSIM 2.6</a><br/>
           <p class="biglink"><a class="biglink" href="https://ndnsim.net/2.5/">ndnSIM 2.5</a><br/>
           <p class="biglink"><a class="biglink" href="https://ndnsim.net/2.4/">ndnSIM 2.4</a><br/>