Missing CI

[galeone]

We have some tests, but we don't run them in the CI.

A TravisCI or something new like GitHub actions must be implemented.

NOTE: some tests require third-party services to be running in the background (e.g. testing the dump of a database, requires the database running and the possibility of calling the DB utils from CLI).

[galeone]

After #10 CI is now present, however, some tests have been disabled because they require some external service to run (e.g. working instance of PostgreSQL and PostgreSQL CLI commands).

This issue will be closed when these tests will be re-enabled and the CI works properly