`strict` keyword doesn't exist in the optimizer's `load_state_dict`

```python
# This works
model.load_state_dict(checkpoint['model_state_dict'], strict=False)

# This gives me "TypeError: load_state_dict() got an unexpected keyword argument 'strict'"
opt.load_state_dict(checkpoint['opt_state_dict'], strict=False)
```
I am using version '0.4.0a0+6dc1fc7'