Update NotificationItem.jsx

Remove of the height reset on render.
This fixes the height of the notification, and prevents having dynamic children (with variable height) to be displayed properly.
Should also help in closing #77.

Author: gnain

src/NotificationItem.jsx

@@ -264,7 +264,7 @@ var NotificationItem = React.createClass({
       }
 
       if (this.state.visible && !this.state.removed) {
-        notificationStyle.height = this._height;
+        //notificationStyle.height = this._height; // this prevents having an automated height when placing high children in notification
         notificationStyle[cssByPos.property] = 0;
       }