Don't update urlhash while in intro

This should cut down on the errant edits in Three Rivers, MI.
Users getting stuck in walkthrough are probably refreshing their browser and
returning to the location in the walkthrough where they got stuck.

app/views/site/id.html.erb

@@ -36,6 +36,7 @@
       });
 
     id.map().on('move.embed', parent.$.throttle(250, function() {
+      if (id.inIntro()) return;
       var zoom = ~~id.map().zoom(),
         center = id.map().center(),
         llz = { lon: center[0], lat: center[1], zoom: zoom };