Update demo notebooks (cubed-dev#525)

* Update demo.ipynb

* Add a note about stats.csv to look at actual memory usage to the examples

* Remove very old example notebooks since they are out of date

examples/README.md

@@ -66,13 +66,20 @@ python matmul-random.py
 
 These will take longer to run as they operate on more data.
 
-The last two examples use `TimelineVisualizationCallback` which produce a plot showing the timeline of events in the task lifecycle.
+The last two examples use `TimelineVisualizationCallback` which produce a plot showing the timeline of events in the task lifecycle, and `HistoryCallback` to produce stats about memory usage.
 The plots are SVG files and are written in the `history` directory in a directory with a timestamp. Open the latest one with
 
 ```shell
 open $(ls -d history/compute-* | tail -1)/timeline.svg
 ```
 
+The memory usage stats are in a CSV file which you can view with
+
+
+```shell
+open $(ls -d history/compute-* | tail -1)/stats.csv
+```
+
 ## Running the notebook examples
 
 Before running these notebook examples, you will need to install some additional dependencies (besides Cubed).