title: ReactJS—mouseOut firing on hover of child element?
body: <p>I've got a div with moueOver and mouseOut functions. 
  Why is the mouseOut firing when I hover over one of the children? This is in a list so I need to use e.target vs. hard coding the '.thumb-overlay'. It's also tweaking the backgrounds of the h2 and h4 inside and I don't quite understand.
  Here is a <a href="https://jsfiddle.net/kirkbross/69z2wepo/48641/" rel="nofollow">FIDDLE</a>.</p>
  
  <pre><code>&lt;div className="thumb-overlay"
   onMouseOver={this.mouseOver.bind(this)}
   onMouseOut={this.mouseOut.bind(this)}&gt;
   &lt;h2&gt;SOME H2 TAG&lt;/h2&gt;  
   &lt;h4&gt;SOME H4 TAG&lt;/h4&gt;
  &lt;/div&gt;
  </code></pre>