Add an optional buildout.cfg

This adds a buildout.cfg for reliable builds via http://buildout.org
Apart from said file, this is purely optional; installation via
pip and setup.py is still supported.

Benefits of using buildout are:
reliable and reproducable builds, project scoped virtualenv/python/ipython,
management of dependencies and console_scripts, ...
Merge pull request #31 from brainbot-com/buildout-cfg

Add an optional buildout.cfg