Add `matches` as an alias of `matchesSelector`.

[According to MDN](https://developer.mozilla.org/en-US/docs/Web/API/Element.matches) `matches` is the standard method name although [older browsers and modern IE implement the same functionality under the method `matchesSelector`](http://caniuse.com/#feat=matchesselector).

This change simply adds `matches` as an alias to `matchesSelector`. I can add a test if desired, but I wasn't sure where to put it. Searching the `test` directory for `matchesSelector` just returned a bunch of jQuery and Sizzle stuff.