SO `chunkWhen` updated for scalaz streams 0.7.3a

ChunkWhen.scala

import scalaz.stream.Process._
import scalaz.stream._
import tee._

object ChunkWhen {
   def chunkWhen[I](f: (I, I) => Boolean): Process1[I, Vector[I]] = {
    def go(acc: Vector[I]): Process1[I,Vector[I]] =
      receive1Or[I, Vector[I]](emit(acc)){ i =>
        acc.lastOption match {
          case Some(last) if ! f(last, i) => emit(acc) ++ go(Vector(i))
          case _ => go(acc :+ i)
        }
      }
    go(Vector())
  }
}