Update update_may_2018.md (#355)

added redirect url

blog/update_may_2018.md

@@ -6,6 +6,7 @@ publish: True
 date: 2018-05-11
 tags: blog, update
 header_img: blog/update_may18/release.png
+redirect_url: https://www.ghostery.com/blog/update-may-2018
 +++
 
 _This post is one of our regular monthly blogs accompanying an update to the data
@@ -122,4 +123,4 @@ largest increase in the average number of trackers per page load was measured in
 
 
 _NB: The code used to generate the data and plots for this post is available in
-[Jupyter Notebook](https://nbviewer.jupyter.org/github/ghostery/whotracks.meblob/master/contrib/wtm_may_update.ipynb)._
+[Jupyter Notebook](https://nbviewer.jupyter.org/github/ghostery/whotracks.meblob/master/contrib/wtm_may_update.ipynb)._