Add support for other CI than Travis

[killy971]

Environment variable reference: https://github.com/codecov/codecov-python/blob/8b9ec3989477c0276158f807a4643d431be288a8/codecov/__init__.py#L82-L148

[wildsebastian]

Jenkins-CI is done.
I am going to add circle-ci soon.
Maybe I can do it until the weekend.

[stevepeak]

@wildsebastian thanks for your help on this. You can see all the CI companies here

[wildsebastian]

Thank you @stevepeak, I already "cheated" these infos from you. ;)
I just created the pull request for CircleCI.

[kutyel]

Hi @wildsebastian, did you manage to make it work on Circle CI? I'm struggling a lot here kutyel/haskell-book@e331e20

[wildsebastian]

@kutyel I think I got it to work, but I can't remember what I did. I might have built a container with everything setup and then just used that container on CircleCI to execute the build and test.

[kutyel]

@wildsebastian I see, if you could check please it would be very helpful, I plan to update the circle CI docs as soon as I have a working solution but right now I haven't been able and it's taking me lots of hours 😄 🙏