IE dynamic CSS-add fix

videojs-youtube has a number of IE compatibility issues, but as long as you only need to support IE8+, most can be fixed with polyfills - namely the following:
classList IE10+
getElementsByClassName IE9+
addEventListener/removeEventListener IE9+

IE versions prior to IE9 don't support style.innerText, and additionally require 'text/sss' mime-type to be set on the element's type property. This requires so little code to fix that I believe it's appropriate to include in the plugin.