dcgan_module

## 🐛 Bug

In the description of dcgan_module.py, it says we can use it on cifar10 as 
```
# cifar10
python dcgan_module.py --gpus 1 --dataset cifar10 --image_channels 3
```

But in the argument parser, it only has two choices: 

```
parser.add_argument("--dataset", default="mnist", type=str, choices=["lsun", "mnist"])
```

Is this a typo? Or the CIFAR10 addition is down the road. 