* Decreasing docker_swarm requirements.
* Fixing docker-py / docker API version requirements, and some comments.
* Add changelog.
* Only send parameters specified by user to docker daemon.
* Extend labels test: not specifying == keep labels.
* Bump minimally required docker-py version for docker_node and docker_node_facts to 2.4.0.
* Prevent crashing when publish or healthcheck is not provided.
* Similarly to docker_swarm tests, only execute docker_node tests on real VMs and restart docker daemon when tests are done.
