Unmunge header names modified by Django.

def _normalize_django_header_name(header):
        """Unmunge header names modified by Django."""
        # Remove HTTP_ prefix.
        new_header = header.rpartition('HTTP_')[2]
        # Camel case and replace _ with -
        new_header = '-'.join(
            x.capitalize() for x in new_header.split('_'))

        return new_header