docs: Update website documentation

Change-Id: I01fa76eabc327a5638627b27bc51e6330d5ad210
Refs: #4213, #4039
diff --git a/docs/source/_templates/indexcontent.html b/docs/source/_templates/indexcontent.html
index 4420c36..f7134ce 100644
--- a/docs/source/_templates/indexcontent.html
+++ b/docs/source/_templates/indexcontent.html
@@ -5,6 +5,7 @@
     <h1>{{ docstitle|e }}</h1>
 
     <p>
+This website includes the ndnSIM documentation and is intended to help the community use the simulator for NDN experimentation. It is not intended to present the principles or the design of the NDN architecture and communication model.
 We invite you to <a href="http://www.lists.cs.ucla.edu/mailman/listinfo/ndnsim" target="_blank">join our mailing list</a> to see and participate in discussions about ndnSIM implementation and simulations in general (<a href="http://www.lists.cs.ucla.edu/pipermail/ndnsim/" target="_blank">mailing list archives</a>).
     </p>
 
@@ -58,8 +59,9 @@
       <td width="50%" valign="top">
         <h2>ndnSIM Versions</h2>
         <div class="tile">
-          <p class="biglink"><a class="biglink" href="#">ndnSIM 2.3</a><br/>
+          <p class="biglink"><a class="biglink" href="#">ndnSIM 2.4</a><br/>
             <span class="linkdescr">latest version</span></p>
+          <p class="biglink"><a class="biglink" href="http://ndnsim.net/2.3/">ndnSIM 2.3</a><br/>
           <p class="biglink"><a class="biglink" href="http://ndnsim.net/2.2/">ndnSIM 2.2</a><br/>
           <p class="biglink"><a class="biglink" href="http://ndnsim.net/2.1/">ndnSIM 2.1</a><br/>
           <p class="biglink"><a class="biglink" href="http://ndnsim.net/2.0/">ndnSIM 2.0</a><br/>
@@ -76,6 +78,9 @@
           <p>If you are referring to ndnSIM in a published work, please cite the following papers, not just the ndnSIM website. Thank you!
           <ul>
             <li>
+              S. Mastorakis, A. Afanasyev, and L. Zhang, "On the Evolution of ndnSIM: an Open-Source Simulator for NDN Experimentation," ACM SIGCOMM Computer Communication Review (CCR), July 2017 (<a class="reference external" href="https://ccronline.sigcomm.org/wp-content/uploads/2017/08/sigcomm-ccr-final112-full-letter.pdf">PDF</a>) (<a class="reference external" href="http://web.cs.ucla.edu/~mastorakis/bibtex-ndnsim">BibTex</a>)
+            </li>
+            <li>
               S. Mastorakis, A. Afanasyev, I. Moiseenko, and L. Zhang, &#8220;ndnSIM 2: An updated NDN simulator for NS-3,&#8221; NDN, Technical Report NDN-0028, Revision 2, 2016 (<a class="reference external" href="https://named-data.net/wp-content/uploads/2016/11/ndn-0028-2-ndnsim-v2.pdf">PDF</a>) (<a class="reference external" href="http://lasr.cs.ucla.edu/afanasyev/bibwiki/bibtex/399">BibTex</a>)
             </li>
             <li>
@@ -97,6 +102,9 @@
           <p class="biglink"><a class="biglink" href="http://www.lists.cs.ucla.edu/mailman/listinfo/ndnsim" target="_blank">ndnSIM mailing list</a><br/>
             <span class="linkdescr"><a href="http://www.lists.cs.ucla.edu/pipermail/ndnsim/" target="_blank">mailing list archives</a></span></p>
 
+          <p class="biglink"><a class="biglink" href="{{ pathto("community-contributions") }}">Community Contributions</a><br/>
+              <span class="linkdescr">very much appreciated contributions of the ndnSIM user community</span></p>
+
           <p class="biglink"><a class="biglink" href="{{ pathto("meta/authors") }}">ndnSIM Team</a></p>
           <p class="biglink"><a class="biglink" href="{{ pathto("meta/copying") }}">Copyright and License</a></p>
         </div>