Trying to fix passing formData from form to middleware

I needed to use 'formData' sent from the client and since the middleware isn't collecting it properly, I tried to make a fix.

This what I did:
Collect formData on 'field' formidable event in UploadHandler.prototype.post method to a req.fields object (created new object if undefined). Extend fileInfo with req.fields on 'end' event. So on upload.on("end", function (fileInfo)), I can have the extra property from formData in fileInfo.

Example use:

In the client:
```html
<form id="formupload" action="/temp" method="post" enctype="multipart/form-data">
	<input type="hidden" name="user_id" value="some user id">
	<input id="fileupload" type="file" name="files[]" data-url="/temp" multiple>
</form>
```

In the server:
```javascript
upload.on("end", function (fileInfo)
	{
		var filemanager = upload.fileManager({
			targetDir: __dirname + "/public/userfiles/" + fileInfo.user_id,
			targetUrl: "/userfiles/" + fileInfo.user_id
		});
		filemanager.move(fileInfo.name, "", function (err, result)
		{
			console.dir(result);
		})
	});
```
I don't see this fix in 0.1.4