Use clojusc/protobuf instead of org.flatland/protobuf for default middleware

[fr33m0nk]

clojusc/protobuf project picked up the Clojure protobuf code base from the ghaskins fork which in turn is a fork of the original but no longer maintained project and has the fix for enums as Clojure keywords amongst many other enhancements.

This removes the need of using any workaround to handle enum declared in protobuf for publishing. Since Ziggurat already offers a default middleware that uses the older protobuf library, updating dependency and code once would be a great solution.

[fr33m0nk]

Please do let me know if I need to update the PR with bumped up version of Ziggurat in project.clj and the change-log

[theanirudhvyas]

Hey @fr33m0nk, thanks for the PR. Have you tested the PR to verify that it is backward compatible with the previous version, i.e. the contract of the middleware hasn't changed?

[fr33m0nk]

Hey @theanirudhvyas ,

Apologies for the delayed reply.

Yeah, I have tested the changes and it indeed is backward compatible.
Middleware contract remains intact and people using this middleware would not be negatively affected if they upgrade.