Allow multiple queues

I'm reading the code in `js_defer_js_alter()`, and it seems like you can't really have more than one queue. For example, look at https://github.com/e0ipso/js_defer/blob/7.x-1.x/js_defer.module#L77-L84. That code is executed outside of the foreach loop, so the value of `$context` and `$deferred_info` will be set to whichever the last item in the array was. Perhaps I am reading it incorrectly?

Start in js_defer.module at js_defer_js_alter(), especially lines 77-84, and trace how $context and $deferred_info are assigned relative to the foreach loop. Reproduce or inspect behavior with more than one queue; done means each queue is handled independently rather than using only the last array item.

Written by the indexing model from the issue text.