Setup WindowsCI

[PragTob]

appveyor is free, I already set it up for shoes back in the day, for elixir one can draw inspiration from nerves

[devonestes]

I briefly tried setting this up, but it would only let me do it for repos I was an owner on. I didn't think setting it up for my fork of Benchee would be very helpful... I'm not sure a non-owner of this repo will be able to do this, unfortunately.

[PragTob]

Not the whole setup no, that's true - but there's an appveyor.yml that helps with all that stuff if someone has it. I planned on doing it myself though, time is a rare commodity these days though :D

[PragTob]

This would be great to have before going 1.0 :)

[PragTob]

I'm gonna give this a go