Add ci.jenkins.io

[vgaidarji]

What has been done

• Replaced Travis CI (https://travis-ci.org/) with Jenkins CI (https://ci.jenkins.io/).
• Preserved Findbugs step (check how others run it on jenkins.io)

Reason

• Building Jenkins plugin on Jenkins (jobs for other plugins on ci.jenkins.io)
• Avoid build limits on Travis - The job exceeded the maximum time limit for jobs, and has been terminated. (failing build)

How to test

https://ci.jenkins.io/ performs a scan of every Jenkins plugin (check the logs here). This is how logs looked like before integration

Proposing fabric-beta-publisher-plugin
22:50:26 GitHub API Usage: Current quota has 1101 remaining (3 under budget). Next quota of 5000 in 13 min
22:50:26 Connecting to https://api.github.com using jenkinsadmin/****** (GitHub access token for jenkinsadmin)
Examining jenkinsci/fabric-beta-publisher-plugin

  Checking branches...
22:50:26 GitHub API Usage: Current quota has 1099 remaining (1 under budget). Next quota of 5000 in 13 min

  Getting remote branches...

    Checking branch master
      ‘Jenkinsfile’ not found
    Does not meet criteria
22:50:26 GitHub API Usage: Current quota has 1097 remaining (1 over budget). Next quota of 5000 in 13 min. Sleeping for 26 sec.
22:50:52 GitHub API Usage: Current quota has 1097 remaining (26 under budget). Next quota of 5000 in 13 min

  1 branches were processed

  Checking pull-requests...
22:50:52 GitHub API Usage: Current quota has 1097 remaining (26 under budget). Next quota of 5000 in 13 min

  Getting remote pull requests...

  0 pull requests were processed

Finished examining jenkinsci/fabric-beta-publisher-plugin

[egor-n]

Thank you for adding Jenkins CI 👍

We should leave Travis too – no harm in that.

[vgaidarji]

https://github.com/jenkinsci/fabric-beta-publisher-plugin/pull/35#issuecomment-429610103 ok, dropped appropriate commit.