Document Vagrant example usage

Closes #30

README.md

@@ -36,6 +36,27 @@ By running `docker-compose up -d`, you will have the api on your local port `300
 
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+## Example projects
+
+A [Vagrantfile](./Vagrantfile) is provided to experiment with `trail`. It will create 5 VMs with multiple docker-based example projects (`wordpress`, `rails`, `django`, a failing `nginx` configuration and a `flog` container).
+
+### Configuration
+
+Install the required `ansible` role (docker installation and configuration) by running the following:
+```bash
+ansible-galaxy install -r requirements.yml
+```
+
+The `LOGSTASH_TARGET` variable in [the provisioning playbook](./provisioning.playbook.yml) is supposed to be modified to suit your needs.
+
+### Running the example projects
+
+In order to use the provisioning part of the [Vagrantfile](./Vagrantfile), simply bring the VMs up and Vagrant will automatically run the corresponding playbook based on the node name.
+
+```bash
+vagrant up
+```
+
 ## Backend
 
 ### Stack