Link demo video from readme

README.md

@@ -9,7 +9,11 @@ Mastodon
 
 Mastodon is a federated microblogging engine. An alternative implementation of the GNU social project. Based on ActivityStreams, Webfinger, PubsubHubbub and Salmon.
 
-![Screenshot](https://i.imgur.com/hzWZdYT.png)
+Click on the screenshot to watch a demo of the UI:
+
+[![Screenshot](https://i.imgur.com/hzWZdYT.png)][youtube_demo]
+
+[youtube_demo]: https://www.youtube.com/watch?v=YO1jQ8_rAMU
 
 Focus of the project on a clean REST API and a good user interface. Ruby on Rails is used for the back-end, while React.js and Redux are used for the dynamic front-end. A static front-end for public resources (profiles and statuses) is also provided.
 
@@ -47,7 +51,7 @@ If you would like, you can [support the development of this project on Patreon][
 - `LOCAL_HTTPS` set it to `true` if HTTPS works on your website. This is used to generate canonical URLs, which is also important when generating and parsing federation-related IDs
 - `HUB_URL` should be the URL of the PubsubHubbub service that your instance is going to use. By default it is the open service of Superfeedr
 
-Consult the example configuration file, `.env.production.sample` for the full list.
+Consult the example configuration file, `.env.production.sample` for the full list. Among other things you need to set details for the SMTP server you are going to use.
 
 ## Requirements
 
@@ -66,11 +70,11 @@ And finally
 
 As usual, the first thing you would need to do would be to run migrations:
 
-    docker-compose run web rake db:migrate
+    docker-compose run web rails db:migrate
 
 And since the instance running in the container will be running in production mode, you need to pre-compile assets:
 
-    docker-compose run web rake assets:precompile
+    docker-compose run web rails assets:precompile
 
 The container has two volumes, for the assets and for user uploads. The default docker-compose.yml maps them to the repository's `public/assets` and `public/system` directories, you may wish to put them somewhere else. Likewise, the PostgreSQL and Redis images have data containers that you may wish to map somewhere where you know how to find them and back them up.
 
@@ -89,3 +93,7 @@ And finally,
     docker-compose up -d
 
 Which will re-create the updated containers, leaving databases and data as is. Depending on what files have been updated, you might need to re-run migrations and asset compilation.
+
+### Contributing
+
+You can open issues for bugs you've found or features you think are missing. You can also submit pull requests to this repository. This section may be updated with more details in the future.