Allow do_lower_case regardless of do_basic_tokenize
It would make sense to me that you could set `do_lower_case=True` even when `do_basic_tokenize=False`. If your input has already been tokenized (but not lower-cased), you still want to lowercase it. As the code is currently written, that does not seem possible as [the BasicTokenizer is responsible for the lowercasing](https://github.com/huggingface/pytorch-pretrained-BERT/blob/master/pytorch_pretrained_bert/tokenization.py#L101-L105):

        if do_basic_tokenize:
          self.basic_tokenizer = BasicTokenizer(do_lower_case=do_lower_case,
                                                never_split=never_split)
        self.wordpiece_tokenizer = WordpieceTokenizer(vocab=self.vocab)
        self.max_len = max_len if max_len is not None else int(1e12)

I would then propose to add lowercase to its own method or to add a do_lower_case to WordpieceTokenizer.

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.
<|||||>@thomwolf Please re-open. If I have the time, I can try to work on this.<|||||>This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.
<|||||>Bump so I don't forget about this.<|||||>This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.
