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
* add basic tutorial, re-export client stuff in HighLevel.Generated
* add a relative link in README.md
* forgot to document the language extensions
* cabal file fixup
* more context to compile-proto-file
* haskell syntax highlighting in markdown
* link to gRPC official tutorials for basic concepts
* add a note on how to build the examples
* prominent notice of required gRPC version
* fix typo
* do some error handling, show how to run the example executables
* use mapM
