styletransfer demo does not work on Windows

[alexisylchan]

evalstyle.ffwd_to_img from StyleTransferDemo fails with the following error on Windows

terminate called after throwing an instance of 'std::bad_alloc'
what():  std::bad_alloc

[alexisylchan]

This commit 4c1e122 partially fixed the issue by using lower resolution images.

Solution:

1. For windows users, pull the latest docker image to get the change above:

   docker pull alexisylchan/introdlcpu-windows

   For others, just pull the latest changes (assuming -recursive doesn't work for you):

    cd introdl
    git pull https://github.com/alexisylchan/introdl.git
    cd demo/styletransfer
    git pull https://github.com/alexisylchan/styletransfer.git

2. Increase docker memory to >5.3 GB https://github.com/docker/dcus-hol-2016/tree/master/docker-developer#advanced-optional