A bunch of files have been missing from the tarballs created by `cabal
sdist`. I’ve changed the nix config to check for this and also found
some examples that I forgot to update in a previous PR (sorry about
that).
* Squash merge from branch `joel-fix-build-issues-and-broken-tests`
* Update `proto3-wire` and `proto3-suite` refs in `stack.yaml`
* Update `proto3-wire` and `proto3-suite` refs via `cabal2nix` for `nix` builds
* Remove `compile-proto-file` from the repo, as it is now available via `proto3-suite`
* Update `proto3-suite` ref in `stack.yaml`
* Update `proto3-suite` ref via `cabal2nix` for `nix` builds
* Update `proto3-suite` and `proto3-wire` gitrevs
* Regenerate Echo and Arithmetic example modules from their respective .protos
* Fix typo
* Update `proto3-suite` gitrev in `stack.yaml` to `8db2ceb8c48a3f8dc2cbdc492d1e8cbaf8b62a15`
* Update `proto3-suite` gitrev in `nix/proto3-suite.nix` to `8db2ceb8c48a3f8dc2cbdc492d1e8cbaf8b62a15`
* Regenerate `Echo.hs` via new `proto3-suite` + `compile-proto-file`
* Remove additional warnings
* echo client/server example: dead code removal, add command line params, improve output messages
* Add nix-build result to .gitignore
* Merge echo-client and echo-server directories to echo-hs/ directory; rename main modules accordingly
* Use our protobuf compiler to generate bindings for the Echo service
* Simplify echo.proto to just one endpoint; use highlevel client/server interfaces and codegen for echo example
* Remove repetition counts and thread spawns from echo client, parameterize payload
* Update default.nix
