CI builds with min & max versions

[Borda]

We have a quite a wide range of supported version but they are not properly tested, so I would like to extend/update CI to be built with minimal and maximal versions defined in requirements.

The limitations now are that Travis build already takes about 20min and adding more test configuration would make finishing it even slower... I was recently playing with GitHub Actions Workflow (I have joined the beta program and they should be released quite soon) and it seems to be quite convenient... I would prepare such testing, but I need @williamFalcon to joint GitHub Action :)

Another alternative would it do it in CircleCI, but GitHub Action has an advantage that it simply supports all three main platforms - Linux, xOS and Win

[Borda]

I would say that having #500 is more important than #502 because the second one aims only on PyTorch compare to the first one aims at complete requirement testing... @williamFalcon