Adding new theme, which is an adaptation of the 'simple' theme. Less fancy and more simplistic.

Hello, 

When I started using oh-my-zsh I was looking for the best theme available. Unfortunately I could not find the perfect one from me, but I found the *simple* theme and it was more close to what I wanted so I patched it and created mine, called *simplest*.

I've taken a screenshot of the theme:

![Simplest theme for oh-my-zsh](http://i.imgur.com/eNFQh.png "Simplest theme for oh-my-zsh")

Please add my theme if you think it deserves to get added to the repo.

Thank you for this project.