Testing documents

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | https://github.com/symfony-cmf/symfony-cmf/issues/191
| License       | MIT
| Doc PR        | -

Seems @WouterJ started this but did not finish. lets see with travis if its all fine.