Persistent server pools (#226)

* GetAllServers with version & timestamp tests
* Storage package to sync servers
* Use storage Sync to get and use servers

docker-compose.yml

@@ -12,6 +12,8 @@ services:
       - 8388:8388/udp # Shadowsocks
       - 8000:8000/tcp # Built-in HTTP control server
     # command:
+    volumes:
+      - /yourpath:/gluetun
     environment:
       # More variables are available, see the readme table
       - VPNSP=private internet access