Test serde::bytes::Bytes and serde::bytes::ByteRef

[TyOverby]

No description provided.

[tikue]

Also, there's an opportunity to be more performant with deserialization of ByteBuf:

fn deserialize_byte_buf<V>(self, visitor: V) -> DeserializeResult<V::Value>
    where V: serde::de::Visitor,
{
    visitor.visit_byte_buf(try!(self.read_vec()))
}