pull / push 3 (並び順の入れ替え)
#1 .col-xs-6 .col-xs-push-6
#2 .col-xs-6 .col-xs-pull-6
#1 .col-xs-4 .col-xs-push-8
#2 .col-xs-4
#3 .col-xs-4 .col-xs-pull-8