Strip out any RTs

[amcewen]

We're getting lots of retweets of our individual weeknote entries now (Yay!), which means there are lots of duplicates to remove from the blog post.

Would be good to spot ones that are just pure RTs, without any differing content, and omit them from the list. We can't just look for "RT", as sometimes they'll be a manual retweet with "#weeknotes" added...