Created by: davidjb
Currently, the divs on the Examples page in v4 don't clear correctly on sm sized screens (eg the Carousel example at http://v4-alpha.getbootstrap.com/examples/#custom-components). The reason for this is the example divs are 6 columns wide on xs and sm devices via .col-xs-6, but the .clearfix after every two examples uses .hidden-sm-up. This results in the .clearfix being hidden on sm devices, where it is needed.
This PR changes hidden-sm-up to hidden-md-up, ensuring the clearfix shows for the xs and sm breakpoints.