Add css-mqpacker for the minified files only.

Without css-mqpacker:

bootstrap-grid.min.css      23.937
bootstrap-reboot.min.css    3.730
bootstrap.min.css           125.440
docs.min.css                23.082

With css-mqpacker:

bootstrap-grid.min.css      23.727
bootstrap-reboot.min.css    3.730
bootstrap.min.css           124.362
docs.min.css                22.406