message: Update readme after unwraps were removed
diff: @@ -278,7 +278,7 @@ into appropriate Rust type:
  ```rust
  use cdrs::error::{Result as CResult};
  -let res_body = parsed.get_body();
  +let res_body = parsed.get_body().unwrap();
  let rows = res_body.into_rows().unwrap();
  let messages: Vec<CResult<Message>> = rows
  .iter()
  @@ -303,7 +303,7 @@ struct Author {
  //...
  use cdrs::error::{Result as CResult};
  -let res_body = parsed.get_body();
  +let res_body = parsed.get_body().unwrap();
  let rows = res_body.into_rows().unwrap();
  let messages: Vec<CAuthor> = rows
  .iter()
  @@ -345,6 +345,7 @@ Prepare-execute query is also supported:
  let executed = session.execute(query_id, execution_params, false, false)
  .unwrap()
  .get_body()
  + .unwrap()
  .into_set_keyspace()
  .unwrap();
  ```
  