Fix path in TF-slim README

The cloned slim directory is found in `$HOME/workspace/models/slim`,
not `$HOME/workspace/slim`.

slim/README.md

@@ -78,7 +78,7 @@ To verify that this has worked, execute the following commands; it should run
 without raising any errors.
 
 ```
-cd $HOME/workspace/slim
+cd $HOME/workspace/models/slim
 python -c "from nets import cifarnet; mynet = cifarnet.cifarnet"
 ```