Modifications to work with pytorch 0.4

[shawntan]

• Removed some Variables
• Modified embedding_dropout so using Functional
• Modified finetune.py loss
• Modified repackage_hidden

[salesforce-cla]

Thanks for the contribution! Before we can merge this, we need @shawntan to sign the Salesforce.com Contributor License Agreement.

[esvhd]

When I tried to run the original code with pytorch 0.4, in addition to the above, I also saw a warning that torch.nn.functional.log_softmax() in splitcross.py should now explicitly specify dim=-1. Any chance we can add this to this PR too?
Thanks.

[esvhd]

Also should add dim=-1 for all torch.nn.functional.softmax(), e.g. in pointer.py.

[keskarnitish]

@shawntan Thank you very much for this. 457a422 makes the repository PyTorch 0.4 compatible.