Allow Vagrant port forwarding to access default dev webserver from host.

Current readme instructions doesn't work for me when access the dev webserver.

I did try experimenting with alternative port forwarding settings, similar to the ones documented at http://docs.vagrantup.com/v2/getting-started/networking.html and the out of box ssh port forwarding, i.e. instead of:

    config.vm.forward_port 8000, 8000

use:

    config.vm.network :forwarded_port, guest: 8000, host: 8000, host_ip: "127.0.0.1"

However this then fails to forward 8000 completely :-(