reduce size of Response, async::Response, and async::Decoder

src/async_impl/body.rs

@@ -1,7 +1,7 @@
 use std::fmt;
 
 use futures::{Stream, Poll, Async};
-use bytes::Bytes;
+use bytes::{Buf, Bytes};
 use hyper::body::Payload;
 
 /// An asynchronous `Stream`.
@@ -88,6 +88,20 @@ pub struct Chunk {
     inner: ::hyper::Chunk,
 }
 
+impl Buf for Chunk {
+    fn bytes(&self) -> &[u8] {
+        self.inner.bytes()
+    }
+
+    fn remaining(&self) -> usize {
+        self.inner.remaining()
+    }
+
+    fn advance(&mut self, n: usize) {
+        self.inner.advance(n);
+    }
+}
+
 impl AsRef<[u8]> for Chunk {
     #[inline]
     fn as_ref(&self) -> &[u8] {