Add acknowledgements in Community section.

content/community.html

@@ -23,11 +23,18 @@
     more elaborate or controversial changes, please discuss them on the mailing
     list before sending a pull request.
   </p>
-  <h1>Sponsorship</h1>
+  <h1>Acknowledgements</h1>
   <p>
     Prometheus was initially started by
     <a href="http://www.matttproud.com">Matt T. Proud</a> and
     <a href="http://juliusv.com">Julius Volz</a>. The majority of its
     development has been sponsored by <a href="https://soundcloud.com">SoundCloud</a>.
   </p>
+  <p>
+    We would also like to acknowledge early contributions by engineers from
+    <a href="https://www.docker.com/">Docker</a> and <a href="http://www.boxever.com/">Boxever</a>.
+  </p>
+  <p>
+    The Prometheus logo was contributed by <a href="http://www.makingstuffmove.com/">Robin Greenwood</a>.
+  </p>
 </div>