Override Bootstrap's default breakpoint for stacking to 1 column. Hopefully we'll be able to change this with a variable in Bootstrap 3.

override-bootstrap-breakpoint.less

@import "mixins.less";
@import "variables.less";

@media (min-width: 400px) and (max-width: 767px) {
  /* Restore standard bootstrap grid for medium-sized devices. */
  #grid > .fluid(@fluidGridColumnWidth768, @fluidGridGutterWidth768);
}