include series count in stats

api/ani/v1/routes/stats.js

@@ -1,5 +1,6 @@
 module.exports = (app, router) => {
     router.get('/stats', (req, res) => res.json({
-        users: Object.keys(app.cache.users).length
+        users: Object.keys(app.cache.users).length,
+        series: Object.keys(app.cache.series).length
     }));
 };