Don't quote MessagePack scalar values at the top level

[nyoung-figly]

It seems like the MessagePack transit writer quotes scalar values at the top level. Reading through the spec: https://github.com/cognitect/transit-format#quoting it seems like there's a good reason for doing this for JSON, but I'm not sure that same reason carries over into MessagePack, especially since users of the binary protocol might be more space conscious?

(def bs (java.io.ByteArrayOutputStream.))
(def writer (transit/writer bs :msgpack))
(transit/write writer 42)
(do (doseq [b (.toByteArray bs)] (printf "%02x " b)) (println))
;; => 92 a3 7e 23 27 2a
;; which is a quoted value, I'd like it to be the single byte 0x2a