title: A scrolling fixed height div in bootstrap column
body: <p>Newbie to Css so hoping this is trivial.</p>
  
  <p>Assume I have a two column, responsive bootstrap 3 grid.  In the left column, I want the column to always fill the height of the browser window, but then within that column I then want a scrollable div to serve up content that is a list much longer than the height of the column it is embedded in.</p>
  
  <p>Make sense?  So far my experiments lead me to the longer div defining the height of its container, which means the entire window scrolls vertically.</p>