Sumo package design - 508

I'm not finished, but here are some notes on why we're doing sumo packages, how we can do them and a bunch of related tasks which may or may not be included in the 0.3 release. 

These notes are mostly based on ideas in:
 * https://hynek.me/articles/python-app-deployment-with-native-packages/

Note: I've branched from my pre-release-rpm branch to pick up the version number function and `admin` package in that branch.

This afternoon I'll try and upload a little prototype code and tests for building RPMs using `fpm`.

Meanwhile:
 * @ryao We can discuss how this fits in with a future sumo flocker-node package for CoreOS 
 * We can also discuss Homebrew  vs building native MacOSX packages (see the notes below)
 * @tomprince We can discuss whether you approve of `fpm` 
 * setting up a debian, gentoo, MacOSX build slave
 * and whether we can automatically update our package repo using buildbot.

Anyway, take a look at what I've written below and see if it makes any sense.

Refs #508
I'm worried about using virtualenv for this, as I've seen cases where minor Python version number upgrades broke existing virtualenvs.