title: Twitter bootstrap need left column rows to split in 2 and contain mid and right cols in md/sm transition
body: <p>I need to nest columns 2-middle and 3-right in between the rows of column1-left's rows on a layout:</p>
  
  <p>I have a layout as such,</p>
  
  <pre><code>column 1      column 2   column 3
  ------        --------   --------
  Image1        Image4     Image6
  Image2&amp;3      Image5     Image7
  </code></pre>
  
  <p>I need it to change to:</p>
  
  <pre><code>col 1
  -------
  Image1
  Image4
  Image5
  Image6
  Image7
  Image2&amp;3
  </code></pre>
  
  <p>at the sm/md boundry</p>
  
  <p>any suggestions, and is there a word for this?</p>