added clone to ByteBuf and BytesMut along with simple clone test

src/buf/byte.rs

@@ -215,3 +215,13 @@ impl fmt::Write for ByteBuf {
         fmt::write(self, args)
     }
 }
+
+impl Clone for ByteBuf {
+    fn clone(&self) -> Self {
+        ByteBuf {
+            mem: self.mem.clone(),
+            rd: self.rd,
+        }
+    }
+}
+

src/bytes.rs

@@ -558,3 +558,16 @@ impl<'a, T: ?Sized> PartialEq<&'a T> for Bytes
         *self == **other
     }
 }
+
+impl Clone for BytesMut {
+    fn clone(&self) -> BytesMut {
+        let mut v = Vec::with_capacity(self.len());
+        v.extend_from_slice(&self[..]);
+        BytesMut {
+            mem: Mem { inner : Arc::new(UnsafeCell::new(v.into_boxed_slice())) },
+            pos: self.pos,
+            len: self.len,
+            cap: self.cap,
+        }
+    }
+}

tests/test_mut_buf.rs

@@ -1,8 +1,9 @@
 extern crate bytes;
 extern crate byteorder;
 
-use bytes::BufMut;
+use bytes::{Buf, BufMut, ByteBuf};
 use std::usize;
+use std::fmt::Write;
 
 #[test]
 fn test_vec_as_mut_buf() {
@@ -45,3 +46,13 @@ fn test_put_u16() {
     buf.put_u16::<byteorder::LittleEndian>(8532);
     assert_eq!(b"\x54\x21", &buf[..]);
 }
+
+#[test]
+fn test_clone() {
+    let mut buf = ByteBuf::with_capacity(100);
+    buf.write_str("this is a test").unwrap();
+    let buf2 = buf.clone();
+
+    buf.write_str(" of our emergecy broadcast system").unwrap();
+    assert_ne!(buf.bytes(), buf2.bytes());
+}