refactors panel borders and adds sul default colors

Fixes #529 

Refactors to mixins the way panel's are colored/bordered

![screen shot 2014-07-28 at 10 47 48 am](https://cloud.githubusercontent.com/assets/1656824/3724728/37efca86-1681-11e4-8ade-be82569c7805.png)
![screen shot 2014-07-28 at 10 50 30 am](https://cloud.githubusercontent.com/assets/1656824/3724729/39c7bdb4-1681-11e4-8e41-29da06916993.png)
![screen shot 2014-07-28 at 10 59 12 am](https://cloud.githubusercontent.com/assets/1656824/3724731/3bbe9408-1681-11e4-8a8b-80ed5a086eeb.png)
![screen shot 2014-07-28 at 10 59 31 am](https://cloud.githubusercontent.com/assets/1656824/3724733/3eba5610-1681-11e4-8b04-b28369642ebd.png)