DataLoader() takes no arguments

I encounter the following error when running the `quick_start/evaluate.py` demo evaluation on my machine.

```
Traceback (most recent call last):
File "quick_start/evaluate.py", line 181, in
model, dataset_reader = run_training_loop()
File "quick_start/evaluate.py", line 162, in run_training_loop
train_loader, dev_loader = build_data_loaders(train_data, dev_data)
File "quick_start/evaluate.py", line 116, in build_data_loaders
train_loader = DataLoader(train_data, batch_size=8, shuffle=True)
TypeError: DataLoader() takes no arguments
```

I believe this is due to generalizing the DataLoader. Possibly `PyTorchDataLoader` should be used instead. Similar code also exists in `quick_start/train.py` and `quick_start/predict.py`.