ci: remove Travis CI workflow

[MikeMcC399]

Issue

• The CI workflow defined by .travis.yml is outdated and unused.
• The README badge links to https://travis-ci.org/indexzero/ps-tree which displays the message "This repository may not exist or you may need to Sign in". The badge itself displays an "unknown" status.
• CI checks on Linux and osx (now macOS) are now carried out with the GitHub Actions workflow ci-test.yml

Change

1. Remove the .travis.yml workflow.
2. Replace the build: status badge in the README file using a badge linked to the functioning GitHub Actions workflow https://github.com/indexzero/ps-tree/actions/workflows/ci-test.yml

Reference

Adding a workflow status badge

Follow-on action

• Check if there is a need to delete any remaining information or account data from https://app.travis-ci.com/indexzero/ps-tree

[nelsonic]

Thanks for removing the .travis.yml file as their service no longer supports older versions of Node.js ✅

[MikeMcC399]

@MikeMcC399

Thanks for removing the .travis.yml file

You are welcome!

as their service no longer supports older versions of Node.js ✅

I believe that Travis CI was failing because there was no longer an active subscription to the service. AFAIK they support all available versions of Node.js, which includes older ones.

[nelsonic]

@MikeMcC399 since Travis CI was sold to Private Equity
https://techcrunch.com/2019/01/23/idera-acquires-travis-ci/ 🤦‍♂️
they have gone downhill and broken the builds of many Open Source projects ... 💔
We had to remove from many repos: dwyl/learn-travis#67 😢
PE has to make their profits/bonuses so they cut the "freeloaders" (that helped build the service...!) ✂️
So now GitHub Actions CI is all we use. ✅

Again, thanks for helping to spring-clean / update this project. 👌

[MikeMcC399]

@nelsonic

Thanks for the background on Travis CI! Now I know why they don't get used in Open Source repos anymore.