Add Vagrant Support

Unit testing is important to continued jQuery development - requiring a bulky local server like WAMP or MAMP in order to run the unit test suite is a huge, unnecessary barrier to entry.  This patch adds a `Vagrantfile` and the necessary provisioning/configuration to spin up a temporary [Vagrant](http://vagranup.com) server with the jQuery project as the web root.

The local Vagrant server can be shut down and/or disposed of just as easily, leaving the developer with a clean local environment after they're done testing.