message: fix tower-h2 example
diff: @@ -3,6 +3,7 @@ extern crate futures;
  extern crate h2;
  extern crate http;
  extern crate tokio;
  +extern crate tokio_current_thread;
  #[macro_use]
  extern crate tokio_trace;
  extern crate tokio_trace_tower_http;
  