Add support to aid with local development and deployment

This changeset includes support for Vagrant, Ansible, and Packer.
Vagrant provides an easy way to spin up local virtual machines, but then
depends on Ansible to provision them. For non-local deployments, Packer
depends on the same playbooks used by Vagrant to generate EC2
AMIs. Those AMIs are then used to launch instances of the GeoTrellis
website.

See the `README` for more details on how to setup a local development
environment, or deploy an updated version of the GeoTrellis website.