fix #1: add cache of latest command to not run wallpaper update when it's already up to date

main.go

@@ -16,18 +16,21 @@ func main() {
 	}
 
 	config, err := LoadConfiguration(os.Args[1])
+
 	if err != nil {
 		log.Printf("[ERROR] %s", err.Error())
 		os.Exit(1)
 	}
 
-	UpdateWallapers(config)
+	var lastCommand string
+
+	UpdateWallapers(config, &lastCommand)
 
 	for recv.Next() {
 		event := recv.Event().(*i3.WorkspaceEvent)
 
 		if event.Change == "focus" {
-			UpdateWallapers(config)
+			UpdateWallapers(config, &lastCommand)
 		}
 	}
 }