title: Possible to convert container/row to container-fluid/row-fluid at viewport breakpoint?
body: <p>For the purpose of learning Bootstrap, I'm copying <a href="http://www.newsweek.com/" rel="noreferrer">http://www.newsweek.com/</a> (using as vanilla Bootstrap as possible) and the top bar (sign in, register, etc.) has me stymied. With a large viewport, it appears to be a simple container/row, but as it resizes and gets to a medium viewport, instead of breaking it seems to transition to a container-fluid/row-fluid. </p>
  
  <p>I set up a tester in Codepen with every possible combination of containers and rows fluid and responsive independent and codependent (that I'm aware of) to figure out what was going on and to experiment a bit: </p>
  
  <p><a href="http://codepen.io/spectre6000/full/vOzeBB/" rel="noreferrer">http://codepen.io/spectre6000/full/vOzeBB/</a></p>
  
  <p>At a 1200px viewport width (as indicated below the rulers),</p>
  
  <pre><code>&lt;div class="container"&gt;
    &lt;div class="row"&gt;
      ...
    &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>and </p>
  
  <pre><code>&lt;div class="container-fluid"&gt;
    &lt;div class="row-fluid"&gt;
      ...
    &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>...are identical. It seems this is what the Newsweek site is doing, but I can't find a way to do it myself without coding the bar twice with different visibility. </p>
  
  <p>How do you switch from one container/row setup to the other at the breakpoint?</p>