Fixed compiler warning.
Added test for Traversable.copyToArray.
Added test for Traversable.fold.
Added test for Traversable.isTraversableAgain.
Added test for Traversable.maxBy.
Added test for Traversable.minBy.
Added test for Traversable.mkString.
Added test for Traversable.product.
Added test for Traversable.reduceLeftOption.
Added test for Traversable.reduceRightOption.
Added test for Traversable.transpose.
Added test for Traversable.unzip3.
Added test for Seq.indexWhere.
Added test for Seq.lastIndexOf.
Added test for Seq.lastIndexOfSlice.
Added test for Seq.lastIndexWhere.