Fix broken links in example documentation. (#732)

doc/source/example-a3c.rst

@@ -9,7 +9,7 @@ View the `code for this example`_.
 
 .. _`A3C`: https://arxiv.org/abs/1602.01783
 .. _`Universe Starter Agent`: https://github.com/openai/universe-starter-agent
-.. _`code for this example`: https://github.com/ray-project/ray/tree/master/examples/a3c
+.. _`code for this example`: https://github.com/ray-project/ray/tree/master/python/ray/rllib/a3c
 
 To run the application, first install **ray** and then some dependencies:
 

doc/source/example-lbfgs.rst

@@ -9,6 +9,10 @@ application, first install these dependencies.
   pip install tensorflow
   pip install scipy
 
+You can view the `code for this example`_.
+
+.. _`code for this example`: https://github.com/ray-project/ray/tree/master/examples/lbfgs
+
 Then you can run the example as follows.
 
 .. code-block:: bash