Max sequence length supported by the library

[huangruizhe]

WER-in-python/wer.py

Line 17 in acefbfc

d = numpy.zeros((len(r)+1)*(len(h)+1), dtype=numpy.uint8).reshape((len(r)+1, len(h)+1))

It would be good to mention in README that the library supports computing WER for sequences up to 256 words. Otherwise, the users need to make the change accordingly.