Bring back Vagrant documentation (fixes #309).

CONTRIBUTING.rst

@@ -27,6 +27,34 @@ The following tools are there to help you:
 
 .. _installing dependencies and setting up Let's Encrypt: https://letsencrypt.readthedocs.org/en/latest/using.html
 
+	
+Vagrant
+=======
+
+If you are a Vagrant user, Let's Encrypt comes with a Vagrantfile that automates
+setting up a development environment in an Ubuntu 14.04 LTS VM. To set it up,
+simply run ``vagrant up``. The repository is synced to ``/vagrant``, so you can
+get started with:
+
+::
+
+	 vagrant ssh
+	 cd /vagrant
+	 ./venv/bin/python setup.py install
+	 sudo ./venv/bin/letsencrypt
+
+Support for other Linux distributions coming soon.
+
+**Note:** Unfortunately, Python distutils and, by extension, setup.py and tox,
+use hard linking quite extensively. Hard linking is not supported by the
+default sync filesystem in Vagrant. As a result, all actions with these
+commands are *significantly slower* in Vagrant. One potential fix is to `use
+NFS`_ (`related issue`_).
+
+.. _use NFS: http://docs.vagrantup.com/v2/synced-folders/nfs.html
+.. _related issue: https://github.com/ClusterHQ/flocker/issues/516
+
+
 CODE COMPONENTS AND LAYOUT
 ==========================