Setup script for Ubuntu/Debian + packer configuration

This script is intended to work on Ubuntu 12.04, Ubuntu 14.04 and Debian Wheezy (for GCE users).
To make sure we use the same version of Redis across all distributions we install from source,
and to make sure we use the same version of PostgreSQL we install it from PostgreSQL's apt.

Also included Packer configuration to generate GCE & AWS images.
Merge pull request #309 from EverythingMe/docs_setup

Setup script for Ubuntu/Debian + packer configuration