title: Add style/class to react-datepicker
body: <p>So basicly how do I add a css class? I've given this a go but it ain't working:</p>
  
  <pre><code>&lt;DatePicker 
         className="form-control 
         dateInput" 
         selected={startDate}  
         onChange={function(date){
                      startDate = date;
                   }
         }
  /&gt;
  </code></pre>
  
  <p>Thanks, Ed.
  (It's been compiled with webpack by the way.)</p>