s/map2/apply2
fix Validation example code
deprecated OptionOps#fold
Merge pull request #488 from xuwei-k/OptionOps-fold

deprecated OptionOps#fold
Zip symmetry law.
EphemeralStream#zip crashed on unequal lengths; fix & test.
Merge branch 'scalaz-seven' of github.com:scalaz/scalaz into topic/zip-laws