Extension to add missing `Map` transformers.

DayOneMapOps.scala

package mapops {
  implicit class DayOneMapOps[A, +B](wrapped: Map[A, B]) {
    // Scalaz has `mapKeys` to just change keys

    // Scala has `mapValues` to just change values

    // Scala has `transform` to just change values but provides key as a parameter

    /**
     * This function transforms all the keys and values of mappings contained in this map with function `f`.
     *
     * @param f A function over keys and values returning a Tuple of new key -> value pair
     * @return the updated map
     */
    def transformAll[C, D, That](f: (A, B) => (C, D))(implicit bf: CanBuildFrom[Map[A, B], (C, D), That]): That = {
      val builder = bf.apply()
      wrapped.foreach { case (oldKey, oldValue) =>
        builder += f(oldKey, oldValue)
      }
      builder.result()
    }

    /**
     * This function transforms all the keys and values of mappings contained in this map with function `f` to
     * a [[scala.Seq]].
     *
     * @param f A function over keys and values returning a single value
     * @return the new [[scala.Seq]]
     */
    def mapToSeq[C](f: (A, B) => C): Seq[C] =
      wrapped.foldRight(Vector.empty[C]) { (pair, result) =>
        val (key, value) = pair
        result :+ f(key, value)
      }
  }
}