add support for docker daemon not running

[soraxas]

For patterns like the following:

$ docker run bash sleep 100
docker: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?.
See 'docker run --help'.

$ fuck
systemctl start docker; and docker run bash sleep 100 [enter/↑/↓/ctrl+c]

[djh82]

Is systemctl O/S specific? i.e. does this work on Windows as well as mac?

Regardless, there are no new tests for this rule and the readme also hasn't been updated.