Adds support for array

Attempt 2: My extension below was wrong.

I would like to be able to do something like:

    var div = $("div.myClass");
    div.find("a").each(...)
    div.find("a.selected").each(...)

However, 
1. There is no support for restricting your dom queries to children of a node via node.querySelectorAll() and returning your class wrapper
2. To add such an extension, I would need the constructor to accept an array of dom nodes as a possible input

So: I can't weigh for you the importance of keeping size down vs supporting array inputs.  What I can show is what my extension looks like:

     $.prototype.find = function(a){
        var result = [];
        this.each(function(node) {
            result = result.concat(Array.prototype.slice.call(node.querySelectorAll(a)));
        });
        return new i(result);
    };

Note: required some hacking to get access to the i() function (grunt build script inserts a module.exports.dom = i)