fix: updating docker compose sample stack and docs according to #135

docker-compose/docker-compose.yaml

@@ -20,6 +20,7 @@ services:
         target: "/var/lib/grafana/dashboards/sample/sample-dashboard.json"
   scaphandre:
     image: hubblo/scaphandre
+    privileged: true
     ports: 
       - "8080:8080"
     volumes:

docs_src/tutorials/docker-compose.md

@@ -7,6 +7,8 @@ Once you have cloned the repository, just move to the docker-compose folder and
     cd docker-compose
     docker-compose up -d
 
+Be warned: the sample stack runs scaphandre as a privileged container. Otherwise apparmor or equivalents might complain about ptrace calls on the host. See [#135](https://github.com/hubblo-org/scaphandre/issues/135).
+
 Grafana will be available at `http://localhost:3000`, the default username is `admin` and the password is `secret`.
 
 Refresh the dashboard after 30s or enable auto-refresh and you should see the data filling the graphs.