Update readme

README.md

@@ -92,6 +92,7 @@ in `~/go/bin/linux_arm`.
       --node-cache-filename=     save and load other nodes information to this file, improves cold start performance
       --node-cache-lifetime=     nodes with last update older than this time (in minutes) will be removed from cache after loading it (default: 1440)
       --node-cache-info          show red and cyan 'x' characters in routes to indicate node cache misses and hits respectively
+  -v, --version                  show program version and exit
 ```
 
 Look in `config.json.sample` or `config.toml.sample` for corresponding keys,