Dont reject the word 'WIP' in commit titles.
Dont reject the word 'WIP' in commit titles.

Changed gitlint rules to not reject the word 'WIP' in commit
titles anymore, since we want to encourage placing this marker
as visible as possible for WIP commits to prevent accidental
merging of a commit that was not considered ready by the
author.

Review: https://reviews.apache.org/r/71837/

dforsyth/mesos,abudnik/mesos,abudnik/mesos,dforsyth/mesos,abudnik/mesos,abudnik/mesos,kaysoky/mesos,dforsyth/mesos,reneploetz/mesos,reneploetz/mesos,Gilbert88/mesos,abudnik/mesos,Gilbert88/mesos,Gilbert88/mesos,reneploetz/mesos,kaysoky/mesos,reneploetz/mesos,dforsyth/mesos,dforsyth/mesos,Gilbert88/mesos,kaysoky/mesos,kaysoky/mesos,kaysoky/mesos,abudnik/mesos,Gilbert88/mesos,Gilbert88/mesos,reneploetz/mesos,kaysoky/mesos,Gilbert88/mesos,reneploetz/mesos,kaysoky/mesos,dforsyth/mesos,reneploetz/mesos,abudnik/mesos,dforsyth/mesos