Allow use of jQuery/dojo for CSS selectors

Turns out selenium doesn't actually augment browser CSS support. Luckily most sites are using jQuery, dojo, or something else that does sane CSS selectors. So I extended webdriverplus to make using third party CSS selectors easy.

This does result in some slowdowns compared to using native browser selectors, so I only really recommend using it when you're using a bad browser (we're using it with IE < 9)