Fix settings.html doesn't return to index.html

Reproduced when the path contains a blank.
Escape('%20') has no effects for this, so 'remote' module is used.

Close #89

src/browser/settings.jsx

@@ -17,7 +17,7 @@ const ListGroupItem = ReactBootstrap.ListGroupItem;
 const Glyphicon = ReactBootstrap.Glyphicon;
 
 function backToIndex() {
-  window.location = 'index.html';
+  remote.getCurrentWindow().loadURL('file://' + __dirname + '/index.html');
 }
 
 var SettingsPage = React.createClass({