Strong preservation law for Zip.
Remove Apply#zip; it yields unlawful Zip instances.
Zip symmetry law.
Merge branch 'scalaz-seven' of github.com:scalaz/scalaz into topic/zip-laws
Revert "Remove Apply#zip; it yields unlawful Zip instances."

This reverts commit e78e6a3c6656d476feb399052344b970f9ca7ef2.
Deprecate Apply#zip.
Laws for Zip; deprecate Apply#zip. (#487)