(Docs) Fixed column ordering example breaking with small grid.

The current example for Column Ordering in the documentation is broken at sizes using the small grid.

This is because the columns become 100% width, but are still offset by +25% (in the case of col-push-3) and -75% (in the case of col-pull-9).

I've added classes to specify the column widths when using the small grid, and everything works fine :)