Upgrade docker-py and improve tests and docs

* Upgraded docker-py to 0.6
* Bumped docker api version to 1.15 and updated tests accordingly
* Made changes that will allow tests to run successfully on OS X
  * boot2docker configuration integration in docker_client function
  * skip platform dependent net-util script runs
* Added README.md documentation
* Added venv to .gitignore
Merge pull request #7 from ibuildthecloud/cj-cleanup

 Upgrade docker-py and improve tests and docs