message: Update README examples after providing tracing
diff: @@ -123,8 +123,9 @@ you need to start Session first.
  ```rust
  let use_query_string = String::from("USE my_namespace;");
  +let with_tracing = false;
  -match session.prepare(use_query_string) {
  +match session.prepare(use_query_string, with_tracing) {
  Ok(set_keyspace) => {
  // use_keyspace is a result frame of type SetKeyspace
  },
  @@ -152,8 +153,9 @@ let mut select_query: Query = QueryBuilder::new("CREATE TABLE keyspace.emp (
  );")
  .consistency(Consistency::One)
  .finalize();
  +let with_tracing = false;
  -let table_created = session.query(select_query).is_ok();
  +let table_created = session.query(select_query, with_tracing).is_ok();
  ```
  @@ -168,8 +170,9 @@ use cdrs::client::Query;
  use cdrs::consistency::Consistency;
  let mut select_query: Query = QueryBuilder::new(use_query.clone()).finalize();
  +let with_tracing = false;
  -match session.query(select_query) {
  +match session.query(select_query, with_tracing) {
  Ok(res) => println!("Result frame: {:?},\nparsed body: {:?}", res, res.get_body());,
  Err(err) => log!(err)
  }
  