feat(*): Scalable registry

Allow the deis registry to be scaled across multiple cluster nodes
feat(CONTRIBUTING): add design proposal guidelines

ripped straight from https://github.com/docker/docker/blob/master/CONTRIBUTING.md#design-and-cleanup-proposals
chore(Makefile): update development registry image to v0.9.0 tag
Merge pull request #2592 from mboersma/bump-dev-registry-0.9.0

chore(Makefile): update development registry image to v0.9.0 tag
Merge pull request #2576 from bacongobbler/design-proposal

feat(CONTRIBUTING): add design proposal guidelines
Merge pull request #2434 from johanneswuerbach/ha-registry

feat(*): Scalable registry
feat(router): include a firewall to mitigate security problems.
ref(router): clean up firewall addition