Convenience wrapper for the excellent formidable node library. Creates and returns a new formidable.IncommingForm for you, optionally specifying a maximum upload size (maxSize);
module.exports = function (req, res, cb, maxSize, formidableOptions)
maxSize and formidableOptions are optional.
Your cb will be invoked as cb(err, fields, files), as specified in .parse in the formidable documentation.