Update index.html

Eventually I want to have 16 of the card image horizontally laid out.
When you click on a card it will flip to show the latent photo.
Atm I can't get the onclick script to work properly. It seems like there
are a few ways of doing it object.click(function(){...} vs. object.onclick=function(){...}
and none are working for me. I've run simpler tests and gotten nothing.