Added Vagrant configuration

This allows starting a Vagrant/VirtualBox linux virtual machine for debugging or testing in a common environment.

To use it:
1. Install Vagrant
2. Install VirtualBox
3. Put sbt-launch.jar into the vagrant directory (later, I'll put a provisioning line in to get it)

vagrant up

vagrant ssh

You're now in a virtual machine with MongoDB running.  You can run sbt to compile/run.  Or if you have run sbt dist, you can unzip the dist and run it.

http://192.168.33.10:9000 will access Impressory on the server.

Don't forget to set environment variables with any social network logins you want configured.  vagrant/.bashrc is gitignored if you want to put them there (but at the moment you will have to call it manually)