`start_instance` now returns a pair (instance_id, variables), so that we can use these variables in the ansible inventory file.
reverted back to using ConfigParser in order to accept multiple configuration files in the future
Remove useless return value for mock class.
Cosmetic changes

Conflicts:
	tests/test_conf.py
Swap public and private ports in get_ssh_ports()
Fix bug: when you assign multiple classes to the same group of nodes, the new ConfigParser object does not split them using the comma character.
Create a `privileged` container. Privileged containers allow you to *unmount* /etc/hosts and to set the hostname of the machine.
Needs docker >= 0.6.2 and docker-py >= 0.2.0
Get the real ip of the container by calling `docker.Client.inspect_container()`
Add regression test