Add version notes

CHANGELOG.md

 # Changelog
 
+## Version 1.3
+
+*January 27th, 2016*
+
+We've upgraded Middleman and a number of other dependencies, which should fix quite a few bugs.
+
+Instead of `rake build` and `rake deploy`, you should now run `bundle exec middleman build --clean` to build your server, and `./deploy.sh` to deploy it to Github Pages.
+
 ## Version 1.2
 
 *June 20, 2015*