Add GitHub workflow and Update badges

[Binnette]

Hi @PanierAvide,

I saw that we (osmlab) no longer have access to travis (seems like we are no fit travis criteria to have free access to its OpenSource plan). So instead of travis, I propose to use GitHub Workflow. I set up a job to run, run tests and publish coverages on coveralls. I tested it on my osm repo.

Before my PR :

After my PR :

Question: should I delete the ".travis.yml" file ???

[PanierAvide]

I saw that nothing in CI worked anymore, but you found out the reason 😁 No problem to switch to GitHub workflow and to remove old CI conf.

[PanierAvide]

Thanks for taking care of the code & repo ☺️