Added rocket hello world code

src/main.rs

@@ -1,3 +1,12 @@
-fn main() {
-    println!("Hello, world!");
+#![feature(proc_macro_hygiene, decl_macro)]
+
+#[macro_use] extern crate rocket;
+
+#[get("/")]
+fn index() -> &'static str {
+    "Hello, world!"
+}
+
+fn main() {
+    rocket::ignite().mount("/", routes![index]).launch();
 }