fixes dragging offset in firefox when scrolling to the end of the page

this is a jquery core issue which still needs to be fixed
this is the suggested hotfix for the problem
the problem can be tracked here:
http://bugs.jqueryui.com/ticket/3740

assets/stylesheets/master_backlog.css

@@ -1,6 +1,7 @@
 #rb #backlogs_container {
   width:100%;
   min-width: 950px;
+  overflow-y: auto;
 }
 #rb #owner_backlogs_container {
   float: right;