Fix a typo in README

>>> with open(filename, 'wt') as f:

>>>     for topic, documents in results.items():

>>>         top_documents = sorted(documents.items(), key=lambda x: x[1], reverse=True)[:1000]

>>>         for rank, (document, similarity_score) in enumerate(top_documents):

>>>         for rank, (document, score) in enumerate(top_documents):

>>>             line = '{}\txxx\t{}\t{}\t{}\txxx'.format(topic, document, rank + 1, score)

>>>             print(line, file=f)

$ git add task1-votes/xnovot32/result.tsv  # track your new result with Git