Create and maintain a CHANGELOG for kd

[KashifSaadat]

Should include details of any breaking changes, kubectl version etc and be referenced with the releases.

[Joseph-Irving]

This would be very nice, especially now you've broken up the releases to be per kube version. Somebody asked me for the changes going from v0.13.0 to v1.10.x and I had to link to a load of different tags.