Add missing package data to setup.py.

Refs #76.

When testing real installations on buildbot, I found that some package data was missing.

http://54.191.63.128/boxes-flocker?branch=missing-package-data
vs.
http://54.191.63.128/boxes-flocker

But there are some intermittent failure: 
http://54.191.63.128/builders/flocker/builds/10/steps/trial/logs/problems
http://54.191.63.128/builders/flocker/builds/8/steps/trial/logs/problems