feat(registry): deis-cache for saving meta data

This improves the registry speed with remote stores and improves the developer UX

Fixes #1780, fixes #1794
If python and Go libraries were shareable, I'm sure that python-etcd would say the same thing (rely on server-side libraries for the right error codes, not the client).

Regardless this value probably won't change so it's not much of an issue keeping as-is.