if two objects are strictly equal, then they are the same object

This fixes https://github.com/busterjs/buster/issues/64 - the elements have some properties which are declared, but undefined. Since there was no check for object sameness, and there is no defined behaviour if `samsam.match(undefined, undefined)` an element was considered non-matching to itself.

Speaking of `undefined`... does it "match" `undefined`? IMHO yes - and I can PR that as well...