In _uihooks, sometimes the `next` argument is null, which means the new dquote> node should be appended to the parent. However, using jQuery
(`$(node).insertBefore(next)`), that's not possible, since jQuery
has no way of knowing what parent you mean.
Instead, this commit uses a standard DOM method,
`parent.insertBefore(node, next)`, which does the right thing --
it's what Blaze uses internally when no `insertElement` hook is
defined.