Bug in jsdom.jQueryify

Haven't had a chance to look at it more closely, but just so I (maybe someone else will take a look at this while I'm working on #792) don't forget.

[This](https://github.com/tmpvar/jsdom/blob/master/lib/jsdom.js#L132) doesn't do what the author wanted it to do. typeof (x === y) will always evaluate to "boolean" which, in context of that if, evaluates to true, which makes the second part of that condition always true.