This is a major rewrite of the Gruntfile which uses a config-driven
approach and leverages grunt-contrib-* plugins to do the heavy lifting.
This creates the build files according to the following conventions:
* `-nr.css`: Rollup `-core.css` + `[module].css` + `-[feature].css`.
* `[module].css`: Rollup `-nr.css` + `-r.css`.
* `-min.css`: A minified file version of the files of the same name.
* `kimono-min.css`: Rollup of all `[module].css` files.
* `kimono-nr-min.css`: Rollup of all modules without `@media`
**Note:** `-r.css` files are not maintained as separate files.
* `-core.css`: The module's most basic functionality.
* `[module].css`: The module's main rules, assumes `-core.css` rules.
* `-context.css`: A contextualized version of `[module].css`.
* `-r.css`: Respnsive, `@media` query rules.
* `-[feature].css`: Optional feature that provides extra rules.
