use element title as navigation select option text when available (#803)

src/plugins/navigation-ui/README.md

@@ -4,6 +4,8 @@ Navigation UI plugin
 This plugin provides UI elements "back", "forward" and a list to select
 a specific slide number.
 
+Element attribut title is used for select option content if available, it uses element id if no title is provided.
+
 The navigation controls are visible if the toolbar plugin is enabled. To add the toolbar to your
 presentations, [see toolbar plugin README](../toolbar/README.md).
 

src/plugins/navigation-ui/navigation-ui.js

@@ -45,7 +45,9 @@
             // Omit steps that are listed as hidden from select widget
             if ( hideSteps.indexOf( steps[ i ] ) < 0 ) {
                 options = options + '<option value="' + steps[ i ].id + '">' + // jshint ignore:line
-                                    steps[ i ].id + '</option>' + '\n'; // jshint ignore:line
+							(
+								steps[ i ].title ? steps[ i ].title : steps[ i ].id
+							) + '</option>' + '\n';
             }
         }
         return options;