Add rust-websocket protocol to client example

This makes the client example compatible with the server one, so one can
run `cargo run --example server` and `cargo run --example client`.

Fixes #114

Author: illegalprime

examples/client.rs

@@ -15,6 +15,7 @@ fn main() {
 
 	let client = ClientBuilder::new(CONNECTION)
 		.unwrap()
+		.add_protocol("rust-websocket")
 		.connect_insecure()
 		.unwrap();