Make the highlight classes more readable

I was playing around with the [Styleguide](https://atom.io/packages/styleguide) today and I noticed that the colored highlight classes were not very readable. This is my attempt at fixing them.

Before:

![screen shot 2014-10-25 at 12 29 35 pm](https://cloud.githubusercontent.com/assets/1038121/4781221/e66723de-5c90-11e4-9d44-f1d6f05116c8.png)

After:

![screen shot 2014-10-25 at 2 44 45 pm](https://cloud.githubusercontent.com/assets/1038121/4781224/eba028c8-5c90-11e4-8d5a-7910647e0638.png)