Minor doc fixes

Minor example change to fix the following error if no parameters are given in behat.yml:

```
Recoverable fatal error: Argument 1 passed to FeatureContext::__construct() must be of the type array,
none given in FeatureContext->__construct() (line 21 of
/opt/development/bdd_travisci/features/bootstrap/FeatureContext.php).
```

Also a minor formatting fix.