Migrate to new CI

[dlebauer]

Travis-CI.org was deprecated in 2021 and no longer builds https://www.travis-ci.org/ e.g. see https://travis-ci.org/github/ebimodeling/ghgvc/builds/751732653

• Could request a free account from Travis-CI.com. They don't appear to have a free plan for academic / open source projects but may be willing to consider a particular request from a small project like this.
• Migrate to GitHub actions (seems to be most popular option since Travis-CI stopped their free tier).

[teixeirak]

Thanks for bringing this up, @dlebauer.

My team has been using GitHub actions a lot lately-- for example: Kim et al. 2022, MEE.

That said, I'm afraid it's just not working to try to publish & maintain the calculator. It would take a fairly large (& growing) push to get it published , and then maintenance & updating to keep up in this rapidly developing field. I don't currently have the time & resources to take care of it.

I hate to pull the plug after investing so much in it, but something would need to change to justify putting more effort into it.