Add the build badge to the nightly build section

downloads.html.haml

@@ -58,7 +58,10 @@ title: Downloads
 
       %p All previous releases can be downloaded from <a href="https://bintray.com/netty/downloads/netty/">here</a>.
 
-      %h3 Nightly builds
+      %h3
+        Nightly builds
+        %a{ :href=>'http://clinker.netty.io/jenkins/job/netty-oraclejdk7/' }
+          %img{ :src=>'http://clinker.netty.io/desktop/plugin/public/status/netty-oraclejdk7', :alt=>'(build status)' }
 
       %p Nightly builds can be found at <a href="http://clinker.netty.io/jenkins/job/netty-oraclejdk7/">our CI server</a>. You can also pull the latest snapshots from <a href="http://clinker.netty.io/nexus/content/repositories/snapshots/io/netty/">our Maven snapshot repository</a>.