ENH(CI): add testing on windows

[yarikoptic]

Required minor refactoring to avoid posixy specification of env variable -- the rest should be ok AFAIK

Inspired by @rly's #31

[djc]

I don't see any actual changes here, only in CI -- is that intended?

[yarikoptic]

yes -- the whole point is to add CI run on windows, no changes to code. But I guess actions are configured not to run from forks to avoid leaking the secret... not sure if you actually even need dedicated COVERALLS token for public repo - should work with

GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

[yarikoptic]

anyways -- there is seems to be more todo since on windows

At D:\a\_temp\95c98458-1671-4858-9895-8f3f1274ea57.ps1:3 char:1
+ pip install flake8 coverage coveralls rply
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[DBG]: PS D:\a\rnc2rng\rnc2rng>> 
Error: The operation was canceled.

although similarly (but in different spots) it gets canceled on ubuntu as well etc... not entirely sure why - may be because other runs failed (due to failing to submit to coveralls).

I guess we could figure out if merged ;)

[djc]

I added Windows CI in #35.

[yarikoptic]

awesome, thank you. IMHO it is a bit suboptimal happen you have some windows/python-version specific code paths, but better than nothing ;) also I would have kept 3.6 tested since AFAIK 3.6 is still supported and it could be quite a surprise if rnc2rng starts to fail on it.

[djc]

Feel free to add it back -- I don't keep up so well with the Python world these days.