BERTConfigs in example usages in `modeling.py` are not OK (?)
Hi!

In the `config` definition https://github.com/huggingface/pytorch-pretrained-BERT/blob/21f0196412115876da1c38652d22d1f7a14b36ff/pytorch_pretrained_bert/modeling.py#L848
in the Example usage of `BertForSequenceClassification` in `modeling.py`, there's things I don't understand:

- `vocab_size` in not an acceptable parameter name, by looking at the `BertConfig` class definition https://github.com/huggingface/pytorch-pretrained-BERT/blob/21f0196412115876da1c38652d22d1f7a14b36ff/pytorch_pretrained_bert/modeling.py#L70

- even by changing `vocab_size` into `vocab_size_or_config_json_file`, for the choice of the other params given in the example i.e.
        ```  
        vocab_size=32000, hidden_size=512, num_hidden_layers=8, num_attention_heads=6,     intermediate_size=1024
        ``` 
I get:
`ValueError: The hidden size (512) is not a multiple of the number of attention heads (6)`
 I think that something similar may be true for the other classes as well, `BertForQuestionAnswering`, `BertForNextSentencePrediction`, etc.

Am I missing something?

Hi @davidefiocco, you are right, I updated the docstrings in the new release 0.3.0.