Feature request: lazy init files

[mfbarrows]

With just

      stream: new RotatingFileStream({
        path: 'logs/error%F.log',
        period: '1d',
      })       

a new empty file is created on each execution, if it doesn't already exist. It would be fantastically helpful if there were an option so that file didn't get created until the first log, so that I can better monitor errors.