Add vagrant for development on other OSes

* Add Vagrantfile for specifying box and networking
* Add vagrant-provision.sh for fleshing out the VM
* Add info on vagrant to HACKING
* Add .vagrant to .gitignore
Tests now run in vagrant; docs updated per reviews.
Merge pull request #41 from makyo/vagrant

* Add Vagrantfile for specifying box and networking
* Add vagrant-provision.sh for fleshing out the VM
* Add info on vagrant to HACKING
* Add .vagrant to .gitignore