Added [A].transform(PartialFunction[A, A]): A, closes #175
Added PartialFunction[A, A].unify: A => A
Added mutable.Builder[A, B] +++= TraversableOnce[TraverableOnce[A]]
Added MultiMap[F, K, V].multiMap.values: F[V]
Added List[A].duplicatesBy[B](A => B): List[A]
Added Map[K, V].mapEntries(K => V => (C, W)): Map[C, W]
Added (A => B => C).tupled: ((A, B)) => C
Added MultiMap[F, K, V].multiMap.mapEntries(K => F[V] => (C, F[W]): MultiMap[F, C, W]
Added List[A].countBy(A => B): MultiMap[List, Int, A]