[bug] start VPN automatically on first launch

When there was no configuration file the 'conf.StartVPN' was set tu
false. Let's set it properly even if there is no config file.

- Resolves: #128

pkg/systray/config.go

@@ -57,12 +57,11 @@ func ParseConfig() *Config {
 	f, err := os.Open(configPath)
 	if err != nil {
 		conf.save()
-		return &conf
+	} else {
+		defer f.Close()
+		dec := json.NewDecoder(f)
+		err = dec.Decode(&conf.file)
 	}
-	defer f.Close()
-
-	dec := json.NewDecoder(f)
-	err = dec.Decode(&conf.file)
 
 	conf.SelectGateway = conf.file.SelectGateway
 	conf.DisableAustostart = conf.file.DisableAustostart