Set up CI/CD pipeline to test the library

[dukenguyenxyz]

Clear used to have a CI/CD pipeline. I don't know for what reason this was removed. But one issue that was present even when we had that pipeline was that sometimes the specs would pass locally but fail on the pipeline - due to environmental differences.

Whatever the case, I think it is necessary we set up the CI/CD pipeline, I've written docker-compose files to wrap around crystal projects with PostgreSQL using clear multiple times before. This PR solves part of the issue #201 , so if you are happy with this idea, @anykeyh , please reply so I can set it up for clear. We can use either travis or github actions, I have used both before, personally I think github action is a better choice.

[anykeyh]

Sorry for late reply. I'm not having a minute for myself until probably March.

I don't understand this issue, there is a travis CI here. Isn't it enough ?