Implement new usage and not modifying Object.prototype

[Gil Lopes Bueno]

new usage:

watch(obj, function(prop, newval, oldval){

});

watch(obj, "prop", function(prop, newval, oldval){

});

watch(obj, ["prop1", "prop2"], function(prop, newval, oldval){

});

[Alex Young]

This is a good idea

[Heitor Salazar Baldelli]

+1

[Heitor Salazar Baldelli]

David Crockford sleeps happier now.
Thank you for the awesome job =D

[Lucca Mordente]

Awesome!

[Gil Lopes Bueno]

Lucca, WatchJS é brasileiro :D

[Lucca Mordente]

Hehe, vi isso num pull request!
@Pickachu também é brasileiro :P
Curtimos demais essa lib, parabéns!

[Gil Lopes Bueno]

Thanks
//lets get back to english haha