Reimplement fmt::Debug for Bytes and BytesMut (#84)

Standard `Debug` implementation for `[u8]` is comma separated list
of numbers. Since large amount of byte strings are in fact ASCII
strings or contain a lot of ASCII strings (e. g. HTTP), it is
convenient to print strings as ASCII when possible.

src/lib.rs

@@ -89,6 +89,7 @@ pub use buf::{
 };
 
 mod bytes;
+mod debug;
 pub use bytes::{Bytes, BytesMut};
 
 pub use byteorder::{ByteOrder, BigEndian, LittleEndian};