Add path option to return uploaded file path

Returning the file upload path, usage sample:

app.use('/api/upload', upload.fileHandler({
  uploadDir: __dirname + '/../public/uploads/'+moment().format('YYYY[/]MM'),
  uploadUrl: '/uploads/'+moment().format('YYYY[/]MM'),
  path: __dirname + '/../public/uploads/'+moment().format('YYYY[/]MM')
}));