feature/vagrant

Adds Vagrantfile and puppet manifests so that a user can easily setup a development environment with a running django server and all the necessary dependencies for both the system and application. Getting the code and development environment should be as easy as this:

```sh
git clone https://github.com/Harvard-ATG/HarvardCards.git 
cd HarvardCards
vagrant up
```

The django server will be running on `http://localhost:8080/`. If any changes are made to the python `requirements.txt` or puppet manifest `manifests/site.pp`, just do a `vagrant provision`.

This was adapted from [django-vagrant](https://github.com/Harvard-ATG/django-vagrant).

Potential improvements for future sprints:
- Setup MySQL and settings config so Django can use that instead of SQLite. 
- Setup Apache or Nginx as the server instead of using the built-in Django server.

@jazahn can you review?