adding my own zenburn theme

There's already a zenburn theme in there, so not sure we NEED two, but by the time I figured out there was one in there I already had the theme and screenshot ready. So whatevs!

CC @an0 What do you think, room for two?  Looks like we have slightly different tastes (I use more of the 'orange' colors). If we want to try and merge them, I'm down with that, too.