add custom theme (l)

This theme is similar to the zsh' "lambda".

![](http://f.cl.ly/items/0K0V220f1P0Y0P1s271S/Untitled.png)
![](https://f.cloud.github.com/assets/501018/62975/ca2de1ac-5da1-11e2-84c4-1784bfc582d0.png)
![Untitled](https://f.cloud.github.com/assets/501018/62976/edd93200-5da1-11e2-8705-518666d07510.png)