Point the issue tracker link to GitHub.

Change-Id: I88cdedea15cc8d459a37507154a61889d043e8cf

docs/source/index.rst

diff --git a/docs/source/index.rst b/docs/source/index.rst
index 0515233..ea9b309 100644
--- a/docs/source/index.rst
+++ b/docs/source/index.rst
@@ -47,8 +47,8 @@
 * Join the `mailing list
   <https://groups.google.com/forum/?fromgroups#!forum/ceres-solver>`_
   and ask questions.
-* File bugs, feature requests in the `issue tracker
-  <https://code.google.com/p/ceres-solver/issues/list>`_.
+* File bugs, feature requests on `GitHub
+  <https://github.com/ceres-solver/ceres-solver/issues>`_.
 
 
 Cite Us