add python 3.9 validation

deliver 1.6.4

deliver 1.6.3 (AmadeusITGroup#100)

remove pytest-runner from setup_requires (AmadeusITGroup#97)

* remove pytest-runner from setup_requires as this is deprecated for security reasons, see * https://github.com/pytest-dev/pytest-runner
* use fixed dependencies in requirements_dev.txt
* cleanup in travis.yml file

fix pypi delivery (AmadeusITGroup#60)

deliver 1.6.0 (AmadeusITGroup#59)

release 1.5.1 (1.5.0 not delivered due to invalid pypi token) (Amadeu…

…sITGroup#48)

Update runSonarQubeAnalysis.sh

Release 1.4.1 (AmadeusITGroup#37)

Release 1.4.0 (AmadeusITGroup#31)