added logging line when using http profile info

I could never remember the url, so I print it out now.

main.go

@@ -46,6 +46,7 @@ func main() {
 		go func() {
 			log.Println(http.ListenAndServe("localhost:8667", nil))
 		}()
+		log.Println("serving profile info at http://localhost:8667/debug/pprof/")
 	}
 
 	games = MapLock{m: make(map[string]*game)}