add some email-contact obfuscation

Author: rubo77

README.md

@@ -14,9 +14,13 @@ Run `backend.py --help` for a quick overview of all available options.
 
 For the script's regular execution add the following to the crontab:
 
-<pre>
+```
 * * * * * backend.py -d /path/to/output -a /path/to/aliases.json --vpn ae:7f:58:7d:6c:2a d2:d0:93:63:f7:da
-</pre>
+```
+
+Since `nodes.json` is distributed wide openly it is recommended to add some email-contact obfuscation:
+
+    sed -i 's/@/(a)/g' /path/to/output/nodes.json 
 
 # Dependencies