Rewrite of the Guestbook example in Go

This is a Go version of the Guestbook example. The readme has been ported over from the existing one.

#1271
Done.

```go
func InfoHandler(rw http.ResponseWriter, req *http.Request) {
	info := HandleError(pool.Get(0).Do("INFO")).([]byte)
	rw.Write(info)
}

func HandleError(result interface{}, err error) (r interface{}) {
	if err != nil {
		panic(err)
	}
	return result
}
```