WIP: setup script for Ubuntu/Debian

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.

This is work-in-progress and published for peer review/contribution. 

TODO:
- [ ] Use pre-made startup script for Redis instead of running `install_server.sh`.
- [ ] Finish sysv init script for supervisor.
- [ ] Config file for supervisor.
- [ ] Test on Ubuntu (currently tested with Debian only).
- [ ] Vagrant box (consider using [packer](http://www.packer.io/docs)).