Allow forwarded_port 4243 to be overridden; Listen on 127.0.0.1 only by default.

The Docker port allows arbitrary remote code execution inside the VM, so
we don't want that turned on by default.

Unfortunately, this is still going to be a problem for users of the
vmware_fusion provider, since it apparently ignores the :host_ip
parameter:

    https://github.com/mitchellh/vagrant/issues/3916

Adding :id => "docker" allows downstream users of the box to disable the
port-forward using something like this in their Vagrantfile:

    config.vm.network "forwarded_port", guest: 4243, host: 4243, id: "docker", disabled: true
Fix Parallels CDROM pre-boot command.
Update to boot2docker 1.0.0.
Merge pull request #52 from dlitz/fix-forwarded-port

Allow forwarded_port 4243 to be overridden; Listen on 127.0.0.1 only by ...
Merge branch 'b2d-1.0.0' into master

Conflicts:
	vagrantfile.tpl
Merge branch 'parallels-cdrom' into master
Update to boot2docker 1.0.1.
Update to boot2docker 1.1.0.
Merge branch 'master' into stable

Conflicts:
	build-iso.sh
Update to boot2docker 1.2.0.
Update README with reference to Parallels support.
Add Makefile to help with building.
fix merge issue