Add Load method to factory

Also update Initialize to take a path to the container
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)
Replace ID with Path on the container
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)
Merge pull request #81 from crosbymichael/update-factory

Add Load method to factory