Update for stepwise processor

Author: samuelleach

Diff for: README.md

@@ -4,3 +4,4 @@ Python notebooks for demonstrating various ideas, APIs, libraries.
 - [planout-abtest](https://github.com/samuelleach/python-notebooks/blob/master/planout-abtest/1.0-planout-abtest-analysis.ipynb) - Defining an AB test experiment with [Planout](https://facebook.github.io/planout/), simulating exposures, and analysing the results.
 - [prophet-uber](https://github.com/samuelleach/python-notebooks/blob/master/prophet-uber/1.0-sl-prophet-uber.ipynb) - Timeseries forecasting of Uber data using [Prophet](https://facebookincubator.github.io/prophet/), which includes a trend, a weekly component and the impact of holidays.
 - [simpy-broadcast](https://github.com/samuelleach/python-notebooks/blob/master/simpy-broadcast/1.0-sl-simpy-message.ipynb) - Demonstration of using [simpy](https://simpy.readthedocs.io/en/latest/) to simulate a stream of read receipts for messages broadcast to 10 recipients.
+- [stepwise-processor](https://github.com/samuelleach/python-notebooks/blob/master/stepwise-processor/1.0-sl-stepwise-processor.ipynb) - Stepwise processor pattern from Mahmoud Hashemi's Enterprise Software with Python course. Demonstrates topic summarization using Wikipedia.