Fixes to allow running keras and crf_baseline models on python 3.7

[ivyleavedtoadflax]

• Minor fixes to crf_baseline and keras code to facilitate running on py3.7
• Add requirements.txt
• Update README.md

[ivyleavedtoadflax]

@Giovanni1085 this should be good to merge if you are happy with it. Currently fixes the crf_baseline and the keras models. I've not yet tried on tensorflow, but since I've added a specific requirements.txt for each, it shouldn't be a problem.

[Giovanni1085]

@ivyleavedtoadflax thank you for your efforts. I had in mind an update to the readme files, not edits to the code directly as this breaks alignment with what we did in the paper, plus the TensorFlow part would remain not updated.

I propose you put the 3.7 code in a separate folder, clearly marked as such, so that people can use it as they see fit. If you agree, please update the pull request accordingly. Alternatively, please feel free to fork and have the 3.7 version under your name. Thank you!

[ivyleavedtoadflax]

How about we commit to a branch name python3.7? That way the code is in your repo, but doesn't interfere with the code as it was in the paper.

[Giovanni1085]

That would be fine for me, but I worry no-one will notice its presence. You could still edit the readme file in the master branch to mention it. Alternatively, why not putting everything in a separate folder on master?

[ivyleavedtoadflax]

Ok sure, I'll create a new folder when i get a moment 👍