lib/common/sitemap.js
function getFile (options, parseFn, callback) {
  fs.readFile(options.source, function (err, data) {
    if (err) {
      callback(common.prependMsgToErr(err, options.source, true));
    } else {
      convert(options, data, parseFn, callback);
    }
  });
}
function getFile (options, parseFn, callback) {
  fs.readFile(options.source, function (err, data) {
    if (err) {
      callback(common.prependMsgToErr(err, options.source, true));
    } else {
      convert(options, data, parseFn, callback);
    }
  });
}
Retrieve the sitemap from a file and call to parse it.

@param {Object} options - Sitemap options.
@param {String} options.source - Sitemap file path.
@param {Function} parseFn - A data parser function.
@param {Function} callback - A completion callback.