Interface to resolve directly with a loaded DOM, avoiding fetching html first

I just used this wonderful library in one project of my own in which I needed an immediate response, avoiding the HTML fetching that some of the plugins require. So I made a quick hack to add a new interface that takes the dom object and avoids the extra call to get the html code and every callback related to it.

I create this pull request so that others are aware of this interface if they need it, or maybe if you @mauricesvay find it useful for a future revision of the API.