Bootstrap 3.2.0

Updated to Bootstrap 3.2.0.

I changed the syntax to be entirely in the nice minimal Stylus style. If you override the Bootstrap variables with your own, you'll need to remove the `$`s.

This version no longer requires nib.

I compared line by line with the Less output and this matches well, with the following differences:
* Some properties will be in a different order
* Some rules are merged (`@extend`)
* Some colors are different (normal Stylus difference)
* Utility classes are in a different order
* Some differences with vendor prefixes. I recommend using `Autoprefixer` as per the official Less version. If someone more knowledgeable with Grunt would like to update the config to include that, it would be much appreciated!