add ci-skip plugin to default list of plugins
add ci-skip plugin to default list of plugins

[ci skip] is used within a commit message to stop a build from running on Jenkins once enables.
To see more information on the implementation. see https://wiki.jenkins-ci.org/display/JENKINS/Ci+Skip+Plugin
medullan/vagrant-ansible-jenkins,medullan/vagrant-ansible-jenkins,medullan/vagrant-ansible-jenkins