Improve release cycle

[meier-rene]

Here are the notes and to does from our webmeeting with @laurentheirendt

• make a dev branch
• improve contribution guidelines (checkout the dev branch, ...)
• push / merge against the dev branch
• merge with master when all tests succeed
• ARTENOLIS could be an alternative to Jenkins CI: https://arxiv.org/pdf/1712.05236.pdf https://prince.lcsb.uni.lu/jenkins/
• hands on:
  • create branch dev and push to it
  • GitHub Branch properties for master, dev: require status checks to pass before merging; include administrators
  • Open pull request > edit > branch is changeable; pass tests; merge
  • tag the 'merge into master' with a release version and comments of the changes