Restrict _.union and _.difference to accept arrays only
Merge branch 'master' of https://github.com/jashkenas/underscore
Tweak a bit, remove failing test.
Merge pull request #1474 from braddunbar/array-methods

Union and Difference Accept Only Arrays
_.now is a utility method.

Alter the docs accordingly.
Merge pull request #1475 from braddunbar/now-utility

_.now is a utility method.
_.partition only accepts arrays.
Merge pull request #1476 from braddunbar/partition-docs

_.partition accepts collections.
Revert "_.partition only accepts arrays."

This reverts commit e4785d38556632d58334616c33292eee95fddfb3.
Merge pull request #1479 from braddunbar/partition

Revert "_.partition only accepts arrays."
Automatically rewritten for npm.