docs: fix broken tutorial link in readme

README.md

@@ -145,7 +145,7 @@ hydra
 
 ### 5 minutes tutorial: Run your very own OAuth2 environment
 
-The **[tutorial](https://ory-am.gitbooks.io/hydra/content/demo.md)** teaches you to set up Hydra,
+The **[tutorial](https://ory-am.gitbooks.io/hydra/content/demo.html)** teaches you to set up Hydra,
 a RethinkDB instance and an exemplary identity provider written in React using docker compose.
 It will take you about 5 minutes to get complete the **[tutorial](https://ory-am.gitbooks.io/hydra/content/demo.html)**.
 
@@ -224,4 +224,4 @@ DATABASE_URL=rethinkdb://localhost:28015/hydra go run main.go host
 A list of extraordinary contributors and [bug hunters](https://github.com/ory-am/hydra/issues/84).
 
 * [Alexander Widerberg (leetal)](https://github.com/leetal) for implementing the prototype RethinkDB adapters.
-* The active Community on Gitter.
+* The active Community on Gitter.