Deploying Symfony in dev environment

I have a staging server that I use to test my application. The issue is if I try setting `:symfony_env, "dev"` I get the following error during the `composer install` phase.

```
[RuntimeException]
An error occurred when executing the "'cache:clear --no-warmup'" command:
PHP Fatal error: Class 'Sensio\Bundle\GeneratorBundle\SensioGeneratorBundle' not found in ../../AppKernel.php on line 40
```

This makes sense, but I don't see in the docs where to override the default `composer install --no-dev --prefer-dist --no-interaction --quiet ...`

Start with the deployment documentation and the composer install command described in the issue, then compare it with the Symfony environment setting and AppKernel.php line 40. Document how to override the default install options for a dev deployment, including the behavior needed to avoid the missing SensioGeneratorBundle error.

Written by the indexing model from the issue text.