add AWS support via Vagrant

This pull request adds AWS support via Vagrant.

Since the docs aren't in code (but in wiki), I'll add the relevant doc once this pull request has been accepted.

For the impatient:

Firstly, install the vagrant-aws plugin, and/or the dummy box:

    vagrant plugin install vagrant-aws
    vagrant box add dummy https://github.com/mitchellh/vagrant-aws/raw/master/dummy.box

Then:

    AWS_ACCESS_KEY_ID="your-aws-access-key" \
    AWS_SECRET_ACCESS_KEY="your-aws-secret-key" \
    AWS_KEYPAIR_NAME="keypair-name" \
    AWS_SSH_PRIVKEY="~/.ssh/keypair-name.pem" \
    AWS_SECURITY_GROUP="name (not ID) of security group that opens ports 22 and 3000 " \
    vagrant up --provider=aws aws

The service will be available at the public DNS for your server, obtainable via the AWS console.