WeTap API Virtual Machine

Download a prebuilt WeTap API virtual machine to ease setting up development environment.

I've snapshotted a fully configured virtualbox and uploaded it to a newly created s3 bucket on our wetap AWS account and registered it with [vagrant cloud](https://vagrantcloud.com/michaelkirk/wetap-api/version/1).

This PR also contains all the automated provisioning to go from the third party base box to a fully functioning WeTap development server (installs rbenv, ruby, bundler, adds postgres user, configuring postgis). The provisioning code isn't pretty, but it works, and if nothing else serves as documentation and a place to start.

See the setup instructions in the README.

@svevang @jmoody do you want to try getting this set up? Should take ~20 minutes, though most of that time will be spent waiting for the 1GB machine image to download.

Also, if you haven't already, you'll have to install [Vagrant](http://www.vagrantup.com/) and [VirtualBox](https://www.virtualbox.org/wiki/Downloads).