Update sorting.html

Ok, so this is the first time I've ever used GitHub so I have no idea how things work here. I changed the slider to a dropdown to pick colors. I think we could possibly put the color name in the actual color that it is, but since I couldn't figure out how to view my changes here I figured I'd let it sit for now. I'll meet up with some people that use GitHub often and get them to walk me through some things over the weekend. If it looks awful just tell EV we have a color dropdown in the works. Sorry!

P.S. I also didn't know what colors they use for their cards so I just threw a small number of sample colors in there.