update Piwik to version 2.16 (fixes #91)

www/analytics/plugins/SEO/Metric/MetricsProvider.php

@@ -0,0 +1,21 @@
+<?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\Plugins\SEO\Metric;
+
+/**
+ * Provides SEO metrics for a domain.
+ */
+interface MetricsProvider
+{
+    /**
+     * @param string $domain
+     * @return Metric[]
+     */
+    public function getMetrics($domain);
+}