Security: OpenSSL::SSL::VERIFY_NONE and some http-only requests

[rmoriz]

• Currently all https/TLS requests are vulnerable to MITM.

  See:

  https://github.com/arangamani/jenkins_api_client/blob/b9a5e5d4ffc0e9240fd3a3d1ff6caeccc611ba92/lib/jenkins_api_client/client.rb#L311-L314

  https://github.com/arangamani/jenkins_api_client/blob/b9a5e5d4ffc0e9240fd3a3d1ff6caeccc611ba92/lib/jenkins_api_client/client.rb#L270-L274

  Suggestion: Change default to verify, allow users who are unable to fix their trust root to set an option to disable verification.

• exec_cli is hard-coded to http:

  https://github.com/arangamani/jenkins_api_client/blob/b9a5e5d4ffc0e9240fd3a3d1ff6caeccc611ba92/lib/jenkins_api_client/client.rb#L617-L619

• update center request is not made over https, too.

  https://github.com/arangamani/jenkins_api_client/blob/b9a5e5d4ffc0e9240fd3a3d1ff6caeccc611ba92/lib/jenkins_api_client/client.rb#L490-L493

[rmoriz]

see #204