Restore commit "vagrant file with some networking update"

This reverts commit 426c57755ba6eda81546604261a4d28cf967277c.

Original was commit 15d5749d6f1f9b678db8c7aefc4a7acc8fd88af4
Author: Sam Joseph <tansaku@gmail.com>
Date:   Fri Jun 6 20:57:32 2014 +0100

It allows a Vagrant VirtualBox host machine to move from
one network to another without restarting the Local Support guest.

http://stackoverflow.com/questions/18457306/enable-internet-access-inside-vagrant
Integrate Vagrantfile changes into upstream
Merge pull request #53 from dcorking/vagrant-networking-tweaks

Vagrant networking tweaks for Sam