Added a Concurrent.joined spec

The new spec proves that Concurrent.joined iteratee breaks early from infinite
enumerators when the target iteratee is done.
Make Cookies extend Traversable.  Add CookiesSpec.
Merge pull request #1609 from jroper/one-joined-spec

Added a Concurrent.joined spec
Merge pull request #1611 from wsargent/1611-cookie-map

Make cookies map public
Merge remote-tracking branch: upstream/master