fix(request): parse_multipart_form should return RequestParameters
fix(request): parse_multipart_form should return RequestParameters

I have this code:

```
form = FileForm(request.files)
```

and it raise error because the `request.files` is `dict` but `RequestParameters` is expected =/
Tim-Erwin/sanic,jrocketfingers/sanic,yunstanford/sanic,Tim-Erwin/sanic,r0fls/sanic,lixxu/sanic,ai0/sanic,channelcat/sanic,ashleysommer/sanic,channelcat/sanic,yunstanford/sanic,channelcat/sanic,ashleysommer/sanic,yunstanford/sanic,r0fls/sanic,lixxu/sanic,channelcat/sanic,yunstanford/sanic,lixxu/sanic,jrocketfingers/sanic,ashleysommer/sanic,ai0/sanic,lixxu/sanic