add link to demo notebook

README.md

@@ -4,7 +4,9 @@
 [![Coverage Status](https://coveralls.io/repos/github/pepkit/eido/badge.svg?branch=master)](https://coveralls.io/github/pepkit/eido?branch=master)
 [![PEP compatible](http://pepkit.github.io/img/PEP-compatible-green.svg)](http://pepkit.github.io)
 
-[PEP](http://pepkit.github.io) validation tool based on [`jsonschema`](https://github.com/Julian/jsonschema) package
+[PEP](http://pepkit.github.io) validation tool based on [`jsonschema`](https://github.com/Julian/jsonschema) package.
+
+See [this jupyter notebook](docs/demo.ipynb) for usage demonstration
 
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 *Eidos* is a Greek term meaning "form" "essence", "type" or "species". See Plato's theory of Forms and Aristotle's theory of universals