Fixing link in README, updates to notebook variable names, small notebook bug fixes

Author: Nathan Silberman

slim/README.md

@@ -13,7 +13,7 @@ converting them
 to TensorFlow's native TFRecord format and reading them in using TF-Slim's
 data reading and queueing utilities. You can easily train any model on any of
 these datasets, as we demonstrate below. We've also included a
-[jupyter notebook](https://github.com/tensorflow/models/tree/master/slim/slim_walkthrough.ipynb),
+[jupyter notebook](https://github.com/tensorflow/models/blob/master/slim/slim_walkthough.ipynb),
 which provides working examples of how to use TF-Slim for image classification.