Update README.rst

Author: Roach

example/README.rst

@@ -90,6 +90,12 @@ If you don't have ngrok, `download it here`_.
 
 .. _download it here: https://roach.ngrok.io/install
 
+
+Here's a rudimentary diagream of how ngrok allows Slack to connect to your server
+
+.. image:: https://cloud.githubusercontent.com/assets/32463/25376866/940435fa-299d-11e7-9ee3-08d9427417f6.png
+
+
 💡  Slack requires event requests be delivered over SSL, so you'll want to
     use the HTTPS URL provided by ngrok.