Add raw driver

```
bash-3.2$ ./boot2docker-v1.1.2-darwin-amd64 --driver=raw --sshhost=10.10.10.2 --sshport=22 --sshkey="" socket
Init raw boot2docker-vm
The 'raw' driver can be used to interact with any already running Boot2Docker based system:
	./boot2docker-v1.1.2-darwin-amd64 --driver=raw --sshhost=10.10.10.19 --sshport=22 --sshkey="" socket
 (it does assume that the vm has 2 connected ethernet ports)
docker@10.10.10.2's password:
docker@10.10.10.2's password:

	 export DOCKER_HOST=tcp://:4243
```
(thats an old Docker 0.8.0 based system with only one network port plugged in)