auto derive codecs for new types from underlying type codecs

Argonautype.scala

import argonaut.{EncodeJson, DecodeJson}
import shapeless._

object Argonautype {

  implicit def EncodeHList[A](implicit encode:EncodeJson[A]):EncodeJson[A :: HNil] =
    encode.contramap(_.head)

  implicit def DecodeHList[A](implicit decode:DecodeJson[A]):DecodeJson[A :: HNil] =
    decode.map(a => a :: HNil)

  implicit def DeriveEncodeNewType[A, R](implicit gen:Generic.Aux[A, R], encode:EncodeJson[R]):EncodeJson[A] =
    encode.contramap(gen.to)

  implicit def DeriveDecodeNewType[A, R](implicit gen:Generic.Aux[A, R], decode:DecodeJson[R]):DecodeJson[A] =
    decode.map(gen.from)
}