Creating convenient syntax for cross-products. From several postings including: https://stackoverflow.com/questions/14740199/cross-product-in-scala and https://stackoverflow.com/questions/2725682/cross-product-of-2-sets-in-scala, but see also https://stackoverflow.com/questions/13567543/cross-product-of-arbitrary-number-of-lists-in-scala for a s…

CrossProduct.scala

implicit class Crossable[X](xs: Traversable[X]) {
  def cross[Y](ys: Traversable[Y]) = for { x <- xs; y <- ys } yield (x, y)
}