Eliminate loading flash for welcome overlay

app/assets/javascripts/index.js

@@ -198,22 +198,19 @@ $(document).ready(function () {
   OSM.Index = function(map) {
     var page = {};
 
-    page.pushstate = function(path) {
+    page.pushstate = function() {
       $("#content").addClass("overlay-sidebar");
       map.invalidateSize({pan: false})
         .panBy([-350, 0], {animate: false});
-      OSM.loadSidebarContent(path);
-      page.load();
     };
 
     page.load = function() {
       return map.getState();
     };
 
-    page.popstate = function(path) {
+    page.popstate = function() {
       $("#content").addClass("overlay-sidebar");
       map.invalidateSize({pan: false});
-      OSM.loadSidebarContent(path);
     };
 
     page.unload = function() {

app/assets/stylesheets/common.css.scss

@@ -649,12 +649,22 @@ nav.secondary {
     }
   }
 
+  .welcome {
+    display: none;
+  }
+
   .overlay-sidebar #sidebar {
     position: absolute;
     z-index: 1000;
     height: auto;
     border-bottom-right-radius: 5px;
     overflow: hidden;
+    .welcome {
+      display: block;
+    }
+    #sidebar_content {
+      display: none;
+    }
   }
 
   .welcome {

app/assets/stylesheets/small.css.scss

@@ -122,7 +122,7 @@ nav.secondary {
 }
 
 #sidebar .welcome {
-  display: none;
+  display: none !important;
 }
 
 .leaflet-top.leaflet-right {