write = function write(filename, result, callback) {
  var content = JSON.stringify(result);
  return zlib.gzip(content, function (err, data) {
    if (err) return callback(err);
    return fs.writeFile(filename, data, callback);
  });
}
Write contents into a compressed file.

@async
@params {String} filename
@params {String} result
@params {Function} callback