* Add difference tracking tool
* Improve --diff mode for docker_container.
* Improve diffs of sets by ordering the sets.
* Rewrite imports, get rid of HAS_DOCKER_PY_x variables and use docker_version instead.
* Rename container -> active (more generic).
* Add --diff for docker_volume. Change old diff output.
* Add --diff for docker_network. Change old diff output.
* Add --diff for docker_swarm_service.
* Add changelog.
* Add entry for porting guide on docker_network and docker_volume.
* Revert change to docker_common as it's not as good as the try: except fix
* limit docker_volume fix to ImportErrors
* fix docker_secret i nthe same way
* Remove docker_secret from import tests
* Added the docker_volume module
* Code style fixes
* Added yours truly to the copyright statement
* Added documentation link
* Fixed YAML syntax in documentation string
* Documentation style fixes based on the code review
* Implemented requested code corrections
* Added documentation for the "labels" option
* Handled APIErrors from docker-py
* Fixed the type of the "labels" option (dict -> list)
* Fixed typo
* Import APIError from docker_common, not from docker-py