update Piwik to version 2.16 (fixes #91)

www/analytics/core/PluginDeactivatedException.php

@@ -0,0 +1,20 @@
+<?php
+/**
+ * Piwik - free/libre analytics platform
+ *
+ * @link http://piwik.org
+ * @license http://www.gnu.org/licenses/gpl-3.0.html GPL v3 or later
+ */
+
+namespace Piwik;
+
+/**
+ * Exception thrown when the requested plugin is not activated in the config file
+ */
+class PluginDeactivatedException extends \Exception
+{
+    public function __construct($module)
+    {
+        parent::__construct("The plugin $module is not enabled. You can activate the plugin on Settings > Plugins page in Piwik.");
+    }
+}