continue to next item if feed is already inserted

I used to skip to the next rss list if the current item is already added, assuming that the following items in the list would have been already added. However, debugging showed that I generally stop the process in the middle of running, so I miss items in the list. Hence the change...
downloading feeds from reversed list
added new model
feed item processed if it is published after the latest item processed

LatestFeed collection is used to store the latest pubDate of the item last processed in the RSS feed. this trick will help me when I start deleting feed item after gist files are created.