code: function initFile(file) {
    if (!file.s3) {
      file.s3 = {};
      file.s3.headers = {};
      file.s3.path = file.relative.replace(/\\/g, '/');
    }
    return file;
  }
docs: init file s3 hash
  @param  {Vinyl} file file object
  
  @return {Vinyl} file
  @api private