adds requirements and python2 hint to README

README.md

@@ -3,6 +3,15 @@
 Fritz InfluxDb is a tiny daemon written in python to fetch data from a fritz box router and writes it to influxdb.
 It is equal capable as fritzcollectd and directly writing to influxdb.
 
+# Requirements
+* python3.6 or newer
+* influxdb
+* fritzconnection >= 1.3.3
+
+## Python 2.7
+If you still need to run it with Python 2 check out the the branch
+[python2.7](https://github.com/yunity/fritzinfluxdb/tree/python2.7)
+
 # Setup
 * here we assume we install in ```/opt```