Returns default filepath for uploaded files.

def uploaded_filepath(instance, filename):
    """
    Returns default filepath for uploaded files.
    """
    ext = filename.split('.')[-1]
    filename = "%s.%s" % (uuid.uuid4(), ext)
    today = datetime.now().strftime('%Y-%m-%d')
    return os.path.join('django-summernote', today, filename)