Updated to be compatible with XHTML and HTML5 polyglot documents

I have modifed coin.js to fix issues that prevented CoinWidget from working with documents served as application/xhtml+xml. This will partially fix #2. I did not implement my changes as a jQuery plugin as suggested by the bug reporter due to the time that would be required to do so.

I also added ALT attributes to the IMG tags to make the widget a little more accessible to people with screen readers.