fix ruby-china#319 图片放大的时候，一旦滑动鼠标一大片白底就露出来了

Author: pmq20

app/assets/javascripts/topics.coffee

@@ -144,6 +144,10 @@ window.TopicView = Backbone.View.extend
     else
       $('a.zoom-image').fluidbox
         overlayColor: "#FFF"
+        closeTrigger: [ {
+          selector: 'window'
+          event: 'scroll'
+        } ]
     true
 
   preview: (body) ->