get(id, options) {
    return this.add(id, options);
  }
Retreives a `winston.Logger` instance for the specified `id`. If
an instance does not exist, one is created.
@param {!string} id - The id of the Logger to get.
@param {?Object} [options] - Options for the Logger instance.
@returns {Logger} - A configured Logger instance with a specified id.