brpc-rs: Write Apache BRPC services in Rust

This is a proof-of-concept and we are adding Rust bindings to Apache RPC.

First please read this to build and install Apache BRPC. brpc-rs dynamically links to libbrpc and libprotobuf.

To run the example: shell $ cargo build --example server $ ./target/debug/examples/server I0605 17:58:25.227115 20975 /home/yjing/incubator-brpc/src/brpc/server.cpp:1039] Server[brpc_rs::HttpServiceImpl] is serving on port=50000. I0605 17:58:25.227269 20975 /home/yjing/incubator-brpc/src/brpc/server.cpp:1042] Check out http://0.0.0.0:50000 in web browser.

Now the demo service is up and running. The BRPC dashboard can be accessed from http://0.0.0.0:50000.

Now let's send some requests to the service. In a separate terminal, run: ```shell $ curl -H "Accept: application/json" --request POST --data '{"name":"Jim","age":12}' http://127.0.0.1:50000/v1/hello {"message":"Hello Jim! You are 12 years old."}%

$ curl -H "Accept: application/json" --request POST --data '24' http://127.0.0.1:50000/v1/hello "24 years old?"% ```