Interoperable $.contains method

[ryanve]

To improve interoperability, it seems wise to alias scan.contains as something else. Currently scan aliases scan.contains as scan.inNode. Maybe scan.descends is a better name?

Compare jQuery.contains vs. _.contains vs "".contains. Something like this combines those:

function contains(ob, needle, i) {
    if (ob.nodeType)
        return inNode(ob, needle);
    i >>= 0;
    if (ob.indexOf)
        return !!~ob.indexOf(needle, i);
    var l = ob.length;
    for (i = 0 > i ? i + l : i; i < l; i++) {
        if (i in ob && ob[i] === needle)
            return true;
    } return false;
}

Yet it seems repetitive to recreate .indexOf functionality here. It is unneeded internally and could be provided (to an ender build, etc.) as needed by a utility module such as underscore, who aliases _.contains as _.include:

function contains(ob, needle, i) {
    return ob.nodeType ? inNode(ob, needle) : this.include(ob, needle, i);
}

_.include also supports checking in non-array-like objects.