update Piwik to version 2.16 (fixes #91)

www/analytics/core/Session/SessionNamespace.php

@@ -1,6 +1,6 @@
 <?php
 /**
- * Piwik - Open source web analytics
+ * Piwik - free/libre analytics platform
  *
  * @link http://piwik.org
  * @license http://www.gnu.org/licenses/gpl-3.0.html GPL v3 or later
@@ -9,6 +9,7 @@
 namespace Piwik\Session;
 
 use Piwik\Common;
+use Piwik\Session;
 use Zend_Session_Namespace;
 
 /**
@@ -28,6 +29,8 @@ class SessionNamespace extends Zend_Session_Namespace
             return;
         }
 
+        Session::start();
+
         parent::__construct($namespace, $singleInstance);
     }
 }