Fix NaN serialization issue

[matthiaskoenig]

Serialization of NaN values if failing again.

        if (_one_shot and c_make_encoder is not None
                and self.indent is None):
            _iterencode = c_make_encoder(
                markers, self.default, _encoder, self.indent,
                self.key_separator, self.item_separator, self.sort_keys,
                self.skipkeys, self.allow_nan)
        else:
            _iterencode = _make_iterencode(
                markers, self.default, _encoder, self.indent, floatstr,
                self.key_separator, self.item_separator, self.sort_keys,
                self.skipkeys, _one_shot)
>       return _iterencode(o, 0)
E       ValueError: Out of range float values are not JSON compliant