func IsGzip(b *bufio.Reader) (bool, error) {
	return CheckBytes(b, []byte{0x1f, 0x8b})
}
IsGzip returns true buffered Reader has the gzip magic.
package xopen
import (
	"bufio"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"os/exec"
	"os/user"
	"strings"
	"compress/gzip"
)