title: Center items in grid layout when not enough data to fill entire row
body: <p>I'm using the new CSS grid layout, basically I'm displaying a series of images, which is fine with six columns, I've gotten that part down, but the content has a variable number, and often times there is not enough content to fill every column, so in the event that there's only say two items in the row, I'd like them to center in the middle two columns. This being a relatively new API though I haven't seen anything like this that I've managed to get working properly. Here is some sample CSS, please excuse my general ignorance if something looks horribly wrong.</p>
  
  <pre><code>#result-images{
  display: grid;
  grid-template-columns: 260px 260px 260px 260px 260px 260px;
  grid-gap: 11px;
  grid-column-gap:55px;
  background-color: #959595;
  border-style:solid;
  border-width:3px;
  border-color:#FFFFFF;
  
  }
  
  #result-images img{
  width:100%;
  height: 100%;
  background-color: #363636;
  display:block;
  margin: 0 auto;
  }
  </code></pre>