Update link to Rietveld project

Change-Id: I412126f5cb6188c3c8e5487a232ba56f02860677

about.md

diff --git a/about.md b/about.md
index 6f4e911..4914dd7 100644
--- a/about.md
+++ b/about.md
@@ -12,7 +12,7 @@
 [Mondrian]: http://video.google.com/videoplay?docid=-8502904076440714866
 [Perforce]: http://www.perforce.com/
 [Bigtable]: http://research.google.com/archive/bigtable.html
-[Rietveld]: http://code.google.com/p/rietveld/
+[Rietveld]: https://github.com/rietveld-codereview/rietveld
 
 ## Rietveld