Added pending tests.
Code reformatting.
Added test for Seq.reverse.
Added test for Traversable.size.
Added test for Traversable.slice.
Added test for Seq.sortWith.
Added test for Traversable.span.
Added test for Traversable.splitAt.
Added test for Traversable.sum.
Added test for Traversable.tail.
Added test for Traversable.take.
Added test for Traversable.takeWhile.
Added test for Set.union.
Added test for Seq.zip.
Added test for Traversable.unzip.
Added test for Traversable.view.
Added test for Seq.zipWithIndex.