Remove travis and appveyor CI config

[danielhuppmann]

Please confirm that this PR has done the following:

• Description in RELEASE_NOTES.md Added

Description of PR

This PR:

• Removes the configuration files for travis and appveyor.
• Badges on the docs pages have been updated (see latest on RTD).
• integration with travis and appveyor has been deactivated.

[stickler-ci]

Could not review pull request. It may be too large, or contain no reviewable changes.

[codecov]

Codecov Report

Merging #409 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #409   +/-   ##
=======================================
  Coverage   93.25%   93.25%           
=======================================
  Files          35       35           
  Lines        4090     4090           
=======================================
  Hits         3814     3814           
  Misses        276      276           

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[danielhuppmann]

@gidden, can you check whether there are any other files or settings that can be removed as part of the migration to GitHub Actions and codecov? thanks!

[gidden]

@znicholls - this would remove files required for the make commands (namely environment files). we were using make test etc on our various CIs, but now this is not needed for github actions.

I think we have three options:

1. remove also the Makefile on which this depends
2. keep the environment files
3. use make in the github actions

I would prefer 1 or 3, as otherwise things will get out of sync. Other preferences?

[znicholls]

Having done this a few times now (see eg github.com/openscm/scmdata or github.com/openscm/openscm-twolayermodel), I’d go for 1. The ultimate source of truth is the CI. The Makefile is a pure convenience but I don’t think you or @danielhuppmann use it so there’s no point keeping it. If I get back into serious development I’ll add it back in but there’s no point having it unless it’s useful.

[danielhuppmann]

thanks @gidden & @znicholls for the input!

[danielhuppmann]

just realized that I'm actually using make publish-on-pypi for every release...

[danielhuppmann]

re-added the environment files needed by make

[znicholls]

https://github.com/danielhuppmann/pyam/pull/16/files fixes up the Makefile so you can remove the ci directory again

[danielhuppmann]

thanks @znicholls for the assist!