Vagrantfile + provisioning script

This does a couple of things:

* creates a virtual machine via [vagrant](http://www.vagrantup.com/) with a static ip (`33.33.33.20`) and a [local hostname](https://github.com/smdahlen/vagrant-hostmanager) (`classcentral.dev`)
* provisions vm with a bash script (cannibalized from an existing symfony project)

If the provision script finds an existing `parameters.yml`, it will also:

* do a composer install of any vendors
* create & load a local database from the sql dump (in `extras` directory)
* run any pending migrations

This should greatly simplify getting a development copy of the project up & running. There's still an issue of incomplete dependancies, see #12