update benches with trait splits

benches/client.rs

@@ -55,6 +55,9 @@ impl hyper::header::Header for Foo {
     fn parse_header(_: &[Vec<u8>]) -> Option<Foo> {
         None
     }
+}
+
+impl hyper::header::HeaderFormat for Foo {
     fn fmt_header(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         "Bar".fmt(fmt)
     }