Change some mercurial/ hg.python.org references. (#8)

diff --git a/Tools/README b/Tools/README
index 73ce6a7..3552881 100644
--- a/Tools/README
+++ b/Tools/README
@@ -43,4 +43,4 @@
                 discovery.
 
 
-(*) A generic benchmark suite is maintained separately at http://hg.python.org/benchmarks/
+(*) A generic benchmark suite is maintained separately at https://github.com/python/performance