Do not work on Windows about winston-s3

[davidbanham]

Thanks for the report! I'm not a Windows user, so could you please help me out by pointing out which aspect of the filename is causing the issue? I'm guessing it's the presence of the : but it might also be the .

[jingzhaoou]

I fixed the issue by changing the following line in winston_s3.coffee.

  return fs.createWriteStream path.join logFilePath, 's3logger_' + (new Date().toISOString()).replace(/:/g, '_')

That is, I replace : with _.

[davidbanham]

Thanks for the report and fix! I've incorporated that and pushed to npm as a new major version since the filenames could be considered an API.