Revert "removed travis support"

This reverts commit 0d8100b1977ea2efe438d6b25a006a56249dd228.
trying to re-add travis
fix travis
fix travis again
fixed travis deps
bump bundle version
fix bundle download
travis: force -lrt
travis: update ubuntu before run tests
travis: remove workarounds that failed. install build-essential
travis: bump bundle version
updated jenkins script
improved jenkins script a bit more
minor fix
added ci badge
jenkins: split test running and dependency installation
removed travis
Merge remote-tracking branch 'origin/master' into feature/sessions