Railscasts (Light) theme

Every hacker knows that a dark background with light text is better for your eyes. So why the Light (background) theme? Because the web (and most OS/application chrome for that matter) uses a light background, and it doesn't look like that's going to change anytime soon. Why be content to only write code in the right color scheme when we read as much code on the web as we write?

My solution is to use the Mac OSX System Preferences > Accessibility > Display > Invert colors option (mappable to a shortcut under Keyboard preferences). Viola! Everything is right with the world. Except for photos, which will be inverted and look weird.

*tl;dr* This pull request includes a Railscasts (Light) theme that is the same as the upstream dark theme, with the colors inverted.