I have written a SharePoint Add-In (June 2015) that performs Auto-Tagging in a smart way. You can find it here:
Follow me on Twitter @stephaneeyskens
This project is the continuity of my two previous projects pertaining to SharePoint which were :
http://sptoolbasket2010.codeplex.com/ (SharePoint 2010)
http://sptoolbasket.codeplex.com/ (SharePoint 2007)
Have a look at the documentation tab to see the details of each release.