[fixed] remove portal context in timeout (#353)

Fixes the binding of the `removePortal` call in the `setTimeout` callback
by capturing a this reference in a variable in the closure scope.
Doesn't use `bind` which apparently causes warnings.

Fixes #344, fixes #348

Author: AndersDJohnson

lib/components/Modal.js

@@ -94,7 +94,8 @@ var Modal = React.createClass({
         this.portal.closeWithTimeout();
       }
 
-      setTimeout(function() { this.removePortal(); }, closesAt - now);
+      var that = this;
+      setTimeout(function() { that.removePortal(); }, closesAt - now);
     } else {
       this.removePortal();
     }