code: function checkCompress(basePath, callback) {
    const gPath = `${basePath}.gz`;
  
    fs.stat(gPath, function(err, stats) {
      if (err || !stats.isFile()) return callback(null, basePath);
  
      callback(null, gPath);
    });
  }
docs: @function checkCompress
  @private
  
  Checks if a gzipped version of a file exists.
  
  @param: basePath {String}
  @param: callback {Function}
  
  If gzipped version exists, callback will be called with the gzipped path.
  If gzipped version doesn't exist, callback will be called with the non-gzipped path.