allow customizing host and port to listen on

doesn't work when not specifying a command, though. to do that
parseCommand would need to know what is an option and what isn't and
react accordingly.

go/linguaevalia/linguaevalia.go

var homePageTemplate = template.Must(template.New("homepage").Parse(homePageTemplateStr))
func runServer() {
	addr, port := "localhost", 8000
	fmt.Printf("running on %s:%d\n", addr, port)
	fmt.Printf("running on %s\n", *address)
	http.HandleFunc("/run", runCodeHandler)
	http.HandleFunc("/codemirror.js", func(w http.ResponseWriter, r *http.Request) {
	})
	http.HandleFunc("/", homePageHandler)
	err := http.ListenAndServe(fmt.Sprintf("%s:%d", addr, port), nil)
	err := http.ListenAndServe(*address, nil)
	if err != nil {
		log.Fatal(err)
	}
}
var language = flag.String("l", "", "The language to use for code passed via stdin.")
var address = flag.String("addr", "localhost:8000", "The host and port to listen on.")
func main() {
	cmd, args := parseCommand()