Update PyTorch API use
Apparently, sketch_simplifaction uses a deprecated/no longer existing module in PyTorch, see [here](https://github.com/pytorch/pytorch/issues/15307) for details.

```
$ python simplify.py
Traceback (most recent call last):
  File "simplify.py", line 4, in <module>
    from torch.utils.serialization import load_lua
ImportError: No module named serialization
```