Update deprecated docker flags to new format
Merge pull request #43 from ruphin/update_docker_flags

Update deprecated docker flags to new format
Document headless VirtualBox and Vagrant config to disable MAC filtering
Improve documentation for macvlan interfaces.
Merge pull request #46 from dineshs-altiscale/vagrant

Document headless VirtualBox and Vagrant config to disable MAC filtering
Update to work with libcontainer

Makes pipework work with the new docker native exec driver (libcontainer).
Use pid from docker inpsect

Since docker returns a pid for the container use that instead of doing all the other hackery.