Infinite loop if iterated over without external stop condition

[smheidrich]

I guess this usually doesn't happen because json-stream quits iterating by itself, but still this is not acceptable:

>>> from json_stream_rs_tokenizer import RustTokenizer
>>> from io import StringIO
>>> r = RustTokenizer(StringIO('1'))
>>> [token for token in r]
[ ... CPU-burning infinite loop, never returns ... ]