Added explicit liaison with Second Screen Presentation CG

Also dropped sentence that said "The Working Group and Community Group will
never work on the same deliverable" since that cannot be guaranteed in
practice.

index.html

@@ -449,8 +449,7 @@ <h3 id="dependencies">
           the Community Group will cease its work on the Presentation API
           specification. It is expected that the Community Group will recharter
           to work on other related deliverables where it is not clear enough how
-          to proceed for it to be a work item for a Working Group. The Working
-          Group and Community Group will never work on the same deliverable. The
+          to proceed for it to be a work item for a Working Group. The
           Community Group is only one possible source for work under future WG
           Charters, but can serve to do initial exploration for some future
           work items.
@@ -515,6 +514,13 @@ <h3 id="liaisons">
             reviews on its deliverables from the Privacy Interest Group to
             ensure they offer the right level of protection to users.
           </dd>
+          <dt><a href="http://www.w3.org/community/webscreens/" id="sspcg">
+            Second Screen Presentation Community Group
+          </a></dt>
+          <dd>
+            This group developed the initial version of the Presentation API
+            and will likely continue to explore new features.
+          </dd>
           <dt><a id="wai" href="http://www.w3.org/WAI/">
             Web Accessibility Initiative</a>
             <a href="http://www.w3.org/WAI/PF/">Protocols and Formats Working