Accept one or more node references as a context

From the jQuery API documentation on the `jQuery` function [1]:

> ## Using DOM elements
>
> The second and third formulations of this function create a jQuery
> object using one or more DOM elements that were already selected in
> some other way.

[1] http://api.jquery.com/jQuery/#using-dom-elements
Merge branch 'pr/343'

Conflicts:
	lib/cheerio.js