added example for multithreaded use

examples/multithreaded_hello.rs

@@ -0,0 +1,12 @@
+extern crate fastcgi;
+
+use std::net::TcpListener;
+
+use std::io::Write;
+use std::thread;
+
+fn main() {
+    fastcgi::run_tcp(|mut req| {
+        thread::spawn(move || write!(&mut req.stdout(), "Content-Type: text/plain\n\nHello, world!"));
+    }, &TcpListener::bind("127.0.0.1:8000").unwrap());
+}