Replace css/sel implementation

Replace the implementation of css/sel with the default
document.querySelectorAll functionality. This fixes an issue with including
goog.dom.query that exports its own namespace even in advanced mode. You can see more detail about the issue on the [ClojureScript list](https://groups.google.com/forum/#!topic/clojurescript/9Tb5jK8cNaY) and then also on the [Google Closure list](https://groups.google.com/forum/#!topic/closure-library-discuss/EZO_fUSYcvU).

From my looking around at [caniuse](http://caniuse.com/#feat=css-sel3), I think the only issue is if someone were to use CSS3 selectors and needed to support IE8. Unfortunately, I think the only workaround would be to modify the code to reference a packaged in version of the goog.dom.query without the namespace exports or to use a different css selector library.