code: function read(file){
  	var fd = fs.readFileSync(file);
  
  	if(isUtf8(fd)){
  		var bf = fs.readFileSync(file);
  	} else {
  		var bf = iconv.encode(iconv.decode(fd, 'gbk'),'utf8');
  	}
  	return bf;
  }
docs: 得到的一定是utf8编码的buffer