cannot import name 'RobertaForTokenClassification'
## 🐛 Bug

<!-- Important information -->

Model I am using (Bert, XLNet....): BERT

Language I am using the model on (English, Chinese....): English

The problem arise when using:
* [x] the official example scripts: (give details) examples/run_ner.py
* [ ] my own modified scripts: (give details)

The tasks I am working on is:
* [x] an official GLUE/SQUaD task: (give the name) NER on CoNLL2003 ENG
* [ ] my own task or dataset: (give details)

## To Reproduce

Steps to reproduce the behavior:

1. $ pip install transformers
2. $ python
3. > from transformers import RobertaConfig, RobertaForTokenClassification, RobertaTokenizer
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: cannot import name 'RobertaForTokenClassification'

<!-- If you have a code sample, error messages, stack traces, please provide it here as well. -->

## Expected behavior

<!-- A clear and concise description of what you expected to happen. -->

## Environment

* OS: Ubuntu 18.04.3
* Python version: 3.6
* PyTorch version: 1.2.0
* PyTorch Transformers version (or branch): pip install transformers
* Using GPU ? Yes, CUDA 10
* Distributed of parallel setup ? No
* Any other relevant information:

## Additional context

<!-- Add any other context about the problem here. -->

+ other bug
  - with '--evaluate_during_training'
```
File "/path-to/run_ner.py", line 167, in train
    results, _ = evaluate(args, model, tokenizer, labels, pad_token_label_id)
TypeError: evaluate() missing 1 required positional argument: 'mode'
```<|||||>- update
  - using `pip3 install git+https://github.com/huggingface/transformers.git --upgrade` command, the first bug got away. <|||||>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.
<|||||>I am also facing the same issue, but even installing from git (as stated by dsindex) did not help.<|||||>It could be because torch is not installed. transformers doesn't install torch automatically but needs the same to load the models. try `pip install torch` and import again!<|||||>I am having the same issue, neither installing from git, nor `pip install torch` have fixed the issue<|||||>Could you provide your software versions, by running `transformers-cli env` in your environment?