README: hint to modern backends

Author: rubo77

README.md

@@ -2,6 +2,13 @@
 
 [![Build Status](https://travis-ci.org/ffnord/ffmap-backend.svg?branch=master)](https://travis-ci.org/ffnord/ffmap-backend)
 
+This is the backend for the old `nodes.json` `v1` format. Please consider using one of the more advanced aproaches that generate `nodes.json` in the new `v2` format or as `meshviewer.json`
+
+ * Yanic: https://github.com/FreifunkBremen/yanic
+ * Hopglass-Server: https://github.com/hopglass/hopglass-server
+
+---
+
 ffmap-backend gathers information on the batman network by invoking :
 
  * batctl (might require root),