Get the name of the most recent log file
@param  {Array}    files
@param  {Function} callback
function getMostRecentFilename (callback) {
  getLogFiles(function (err, files) {
    if (err) {
      callback(err, null);
    } else if (!files || files.length === 0) {
      return callback(null, Date.now().toString().concat(FILE_EXT));
    } else {
      var file = _.max(files, function (f) {
        var n = (f && typeof f.name === 'string') ? f.name : f;

        // Remove extension to get just the timestamp
        var ts = n.replace(FILE_EXT, '');

        return parseInt(ts, 10);
      });

      var n = (file && typeof file.name === 'string') ? file.name : file;

      callback(null, n);
    }
  });
}