good first issue: python 2.7 to python 3.x

Good first issue: translate everything from python 2.7 to python 3.x.

Could be that it simply needs commands like:

```
git checkout -b py3
2to3-3.5 -w compare.py
git diff
```
for each of the `.py` files in this repo.

But perhaps it then also needs some tweaking, because the interfaces of the libraries have had breaking changes?

We don't know - until you try.

Thanks.