add piwik installation

www/analytics/core/Tracker/VisitInterface.php

@@ -0,0 +1,32 @@
+<?php
+/**
+ * Piwik - Open source web analytics
+ *
+ * @link http://piwik.org
+ * @license http://www.gnu.org/licenses/gpl-3.0.html GPL v3 or later
+ *
+ */
+
+namespace Piwik\Tracker;
+
+/**
+ * Interface implemented by classes that track visit information for the Tracker.
+ * 
+ */
+interface VisitInterface
+{
+    /**
+     * Stores the object describing the current tracking request.
+     * 
+     * @param Request $request
+     * @return void
+     */
+    public function setRequest(Request $request);
+
+    /**
+     * Tracks a visit.
+     * 
+     * @return void
+     */
+    public function handle();
+}