Fix link to examples directory

When the examples link was added to the readme, there was only one
example, so it made sense to link to it directly. Later, a second
example was added.

This updates the link so it points to the directory rather than a
specific module in it.

README.md

@@ -13,7 +13,7 @@ pip install npc-gzip
 
 ## Usage
 
-See the [examples](./examples/imdb.py) directory for example usage.
+See the [examples](./examples/) directory for example usage.
 
 ## Testing