support running on $PORT

go/favicon.go

	"github.com/golang/groupcache/lru"
)
var port = "8080"
var faviconCache = lru.New(10000)
var lock sync.RWMutex
func main() {
	http.HandleFunc("/favicon", HandleGetFavicon)
	err := http.ListenAndServe(":8080", nil)
	if p := os.Getenv("PORT"); p != "" {
		port = p
	}
	fmt.Printf("listening on :%s\n", port)
	err := http.ListenAndServe(fmt.Sprintf(":%s", port), nil)
	if err != nil {
		fmt.Println("error: ", err)