Improve to bring closer to Vim Zenburn theme

[ryanolsonx]

Hello there!

I've been working on a Sublime Text port of Zenburn (from the original Vim color scheme). It supports a ton of languages and is pretty dang close to the Vim version.

In my package control PR, they suggested that I talk to you about incorporating my changes here. I think they're hoping to avoid 2 Zenburn color schemes in Package Control.

If I created a PR here, would you be open to working with me to merge it in?

All-in-all, I'm a big fan of Zenburn and would love to help improve your package. :D