title: Center div vertically in flexbox container with stretch alignment
body: <p>I need to center a div in flex container with keeping the height of the whole container for that div. Obviously, I have <code>align-items:stretch</code> for keeping a height or <code>align-items:center</code> for centering block. What is a good approach for flexbox model to center a div with keeping height of the parent container?</p>
  
  <p>JSFiddle: <a href="http://jsfiddle.net/symb8s02/" rel="nofollow">http://jsfiddle.net/symb8s02/</a></p>