tests: add build status for master branch in README

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
tests: update Jenkins badge link in README

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
documentation: move credits at the end

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>