Added Solarized Light theme.

Hello! This commit adds a light theme based off of [Solarized](http://ethanschoonover.com/solarized) and the base Tasks theme. Here's a screenshot:

![image](https://f.cloud.github.com/assets/69549/1688304/d5a735d8-5e04-11e3-8b51-f23b006079f9.png)

I've tried to stay true to the intentions of both Solarized and Tasks. I'm certainly open to suggestions for ways this can be made better.