Fixes the following issue:
(1) Use recent Docker client library
$ containers-ps panic: Error response from daemon: client version 1.37 is too old. Minimum supported API version is 1.40, please upgrade your client to a newer version
(2) Document dependencies
$ make cmd/containersps/containersps.go:5:2: no required module provides package devcentral.nasqueron.org/source/docker-processes/pkg/dockerutils: go.mod file not found in current directory or any parent directory; see 'go help modules'