Stub generator for grpc.
Library and `protoc-gen-rust-grpc` plugin for `protoc`.
Can be installed with command `cargo install grpc-compiler`.
Alternatively, [protoc-grpc-rust](https://github.com/stepancheg/grpc-rust/tree/master/protoc-rust-grpc)
crate can be used to invoke codegen programmatically, which only requires `protoc` command in `$PATH`.