Style and documentation tests take just a few minutes
to run. Since in Github actions one can't restart a single
job but needs to restart an entire workflow, here we group
tests with similar duration together.
* Move flake8 tests on Github Actions
* Move shell test to Github Actions
* Moved documentation build to Github Action
* Don't run coverage on Python 2.6
Since we get connection errors consistently on Travis
when trying to upload coverage results for Python 2.6,
avoid computing coverage entirely to speed-up tests.
* Added unit tests to Github Actions
* Set user e-mail and name for git tests to succeed
* Simplify setup.sh logic
* Replicate Travis script on Github Actions
* Update flags since '.' is not allowed
* Added badge, simplified workflow
* Remove pinning of coverage
* Remove unit tests run on Github Actions from Travis
