fix tiny typo

Nice collection, thanks for sharing it. By the way, I thought that by clicking on the the SHA hash in your blog's right sidebar for [this post](http://www.carlboettiger.info/2014/01/02/open-science-literature-highlights.html) would take me to the source of that post for convienent editing. But the hash was 90ecb182cfe862b87eb74c06333fa9d9b403e3fd which linked me to [a different blog entry](https://github.com/cboettig/labnotebook/commit/90ecb182cfe862b87eb74c06333fa9d9b403e3fd/_posts/2014-01-02-open-science-literature-highlights.md). Having a quick survey of other posts on your blog, the SHA hash link often doesn't link to the code for the post. Am I misunderstanding the meaning of that SHA hash link?