Add stacklayout

[StackLayout](http://www.stacklayout.com/) seems to be a pretty solid framework. Right from their readme:
```
StackLayout uses display:inline-block with negative letter spacing
in a fixed width font (Courier New) in order to achieve a 
floatless, gridless layout system, the components of which can 
be nested within each other to produce virtually any layout.
```

Seems like it'd be a good addition, but it may be too "different".