We want to be compatible with whatever docker the user has; `weave
run` is the only command that passes on arbitrary args to docker
(i.e., that doesn't have a fixed set of docker features that it
needs).
To make this workable we still need to do some things on the remote
host: the IP attachment and figuring out the DNS settings (since those
may depend on the bridge IP).
* disable the default Vagrant shared folder, which we don't need
* install `bc` on the dev VM, since it's needed by the smoke tests
* expose the dev VM docker on TCP, for convenience
Michael Bridgen