Killing ZeroClipboard.$ selector :skull:

The `ZeroClipboard.$` is really just a small hack written into the library to try and support something that js libraries and browsers do really well.

Our implementation of it however was a half-measure. While we did accept some query strings, we didn't have advanced features like context searching that larger libraries do support.

Rather than try and rebuild what is already great, we want to be really great at putting text into a clipboard. And that's it.

So this pull request removes the selector engine, and accepts an element or array of elements directly. Leaving the searching up to the developer.

Discussion on this began in #60 #61 

@JamesMGreene @domchristie @tjdhome