Use Bert model without pretrained weights
Hi,
I wanted to train a Bert classifier from scratch without any pretrained weights.  It has to be randomly initialized and trained. 

Example:
```
bert_base_model = BertForSequenceClassification()
trainer = Trainer(model=bert_base_model,
                  args=training_args,
                  train_dataset=train_loader,
                  eval_dataset=test_loader,
                  compute_metrics=compute_metrics
                  )
```
If you want to train it from scratch you can use `BertConfig`, something like this:-

```python
from transformers import BertConfig, BertForSequenceClassification

config = BertConfig() # You can also change the architecture using this config class

model = BertForSequenceClassification(config=config)
```

Then you can proceed using the Trainer class to train the model.<|||||>thank you
I initially tried with this
```
bert_base_model = BertForSequenceClassification(BertConfig)
```
I was getting error.