Remove piwik tracker, it is no longer being used.

R1/source/_templates/navigation.html

@@ -54,18 +54,3 @@
   ga('create', 'UA-16257769-1', 'auto');
   ga('send', 'pageview');
 </script>
-<!-- Piwik -->
-<script type="text/javascript">
-    var _paq = _paq || [];
-    _paq.push(['trackPageView']);
-    _paq.push(['enableLinkTracking']);
-    (function() {
-    var u="//varnishcache.piwikpro.com/";
-    _paq.push(['setTrackerUrl', u+'piwik.php']);
-    _paq.push(['setSiteId', 1]);
-    var d=document, g=d.createElement('script'), s=d.getElementsByTagName('script')[0];
-    g.type='text/javascript'; g.async=true; g.defer=true; g.src=u+'piwik.js'; s.parentNode.insertBefore(g,s);
-    })();
-    </script>
-<noscript><p><img src="//varnishcache.piwikpro.com/piwik.php?idsite=1" style="border:0;" alt="" /></p></noscript>
-<!-- End Piwik Code -->