Update docs to support docker swarm

- again, copy from go

Closes #67
3 jobs for 67-docker-swarm in 1 minute and 35 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #3645
whats-open-py2.7

00:01:29

passed #3646
whats-open-py3.5

00:01:34

passed #3647
whats-open-py3.6

00:01:35