Fix a bug where expires option was not setting cookie expiration date.

'extends', when compiled to CoffeeScript, was returning an array of
arrays rather than an object due to implicit return.  This caused
the 'expires' attribute of the returned options object to always be
undefined, so the cookie expiration field was never set as
options.expires.toGMTString().

This bug also caused abbaVariant and abbaPersistComplete cookies to
incorrectly have no expiration date or a default expiration date,
rather than the 600 day expiration as specified in the code.