Update documentation to refer to 1.7.0

Change-Id: I95f131f36ec1e86f9132e9bfc4341a524c603579

docs/source/index.rst

diff --git a/docs/source/index.rst b/docs/source/index.rst
index f20dad4..21476fe 100644
--- a/docs/source/index.rst
+++ b/docs/source/index.rst
@@ -11,7 +11,7 @@
 squares problems.
 
 * Download the latest stable `release
-  <https://ceres-solver.googlecode.com/files/ceres-solver-1.6.0.tar.gz>`_
+  <https://ceres-solver.googlecode.com/files/ceres-solver-1.7.0.tar.gz>`_
   or clone the `repository
   <https://ceres-solver.googlesource.com/ceres-solver>`_