Refactored django exaple

Refactored example of Ferdinand Silva
- Use buffered writer for store file( with this we may get size of data "on-the-fly")
- Remove META["CONTENT_LENGTH"] from code('cause it's not a real file size)
- Correctly get filename if request is POST

This code is correctly work in production with django 1.5 and 1.6-dev, and with FileUploader 3.3

Thanks for you job, guys!