WIP: Spark development environment

The primary goal of this pull request is to support a Spark development environment with the existing EC2 Ansible playbooks. The entire development environment exists within Vagrant virtual machines (`1` for the Spark master, and `2` for the Spark workers, thus far).

**Usage**

```bash
$ cd scripts/deploy-ec2
$ cp group_vars/all.yml.example group_vars/all.yml
$ cp group_vars/development.yml.example group_vars/development.yml
$ vagrant up
$ open http://33.33.33.10:18080/
```