PR template: make changelog entry obligatory
PR template: make changelog entry obligatory

surdy/dcos,dcos/dcos,surdy/dcos,dcos/dcos,amitaekbote/dcos,mesosphere-mergebot/dcos,surdy/dcos,mesosphere-mergebot/dcos,kensipe/dcos,mesosphere-mergebot/dcos,GoelDeepak/dcos,GoelDeepak/dcos,mesosphere-mergebot/dcos,dcos/dcos,amitaekbote/dcos,mesosphere-mergebot/mergebot-test-dcos,mesosphere-mergebot/mergebot-test-dcos,kensipe/dcos,amitaekbote/dcos,amitaekbote/dcos,kensipe/dcos,dcos/dcos,GoelDeepak/dcos,GoelDeepak/dcos,surdy/dcos,kensipe/dcos,mesosphere-mergebot/mergebot-test-dcos,mesosphere-mergebot/mergebot-test-dcos,dcos/dcos