Merge pull request #534 from bjhargrave/master

Further clean up of bnd repo
readme: Remove some old info

Signed-off-by: BJ Hargrave <bj@bjhargrave.com>
contributing: Define contribution rules and triangular workflow

We have moved to a triangular workflow for bnd. This document describes
the workflow and how to set it up.

Credit to docker for the contributing document.
https://github.com/dotcloud/docker/blob/master/CONTRIBUTING.md

Signed-off-by: BJ Hargrave <bj@bjhargrave.com>