Remove .bind(this) from removePortal call

This fixes this warning from react in the console without breaking functionality:

Warning: bind(): You are binding a component method to the component. React does this for you automatically in a high-performance way, so you can safely remove this call. See Modal

lib/components/Modal.js

@@ -94,7 +94,7 @@ var Modal = React.createClass({
         this.portal.closeWithTimeout();
       }
 
-      setTimeout(this.removePortal.bind(this), closesAt - now);
+      setTimeout(function() { this.removePortal(); }, closesAt - now);
     } else {
       this.removePortal();
     }