Update the script to work with pytorch v0.4

[dansuh17]

apply possible API changes

 model.py:254: UserWarning: nn.init.xavier_normal is now deprecated in favor of nn.init.xavier_normal_.
model.py:389: UserWarning: nn.init.normal is now deprecated in favor of nn.init.normal_

2018-06-26 13:56:18,462 STDOUT model.py:430: UserWarning: invalid index of a 0-dim tensor. This will be an error in PyTorch 0.5. Use tensor.item() to convert a 0-dim tensor to a Python number                                             
2018-06-26 13:56:18,463 STDOUT   epoch + 1, i + 1, clean_loss.data[0],                                                
2018-06-26 13:56:18,463 STDOUT model.py:431: UserWarning: invalid index of a 0-dim tensor. This will be an error in PyTorch 0.5. Use tensor.item() to convert a 0-dim tensor to a Python number

[dansuh17]

done.