Stability issue

Currently it is not possible that via the default way

```
composer require "gnugat/wizard-bundle:~1"
```

from the installer a newer version than 1.0.1 could be installed.

The newer versions are marked as alpha because of the [@alpha requirement of composer](https://github.com/gnugat/GnugatWizardBundle/blob/master/composer.json#L17) and thus they will not be taken into account for projects with `minimum-stability: stable`.

This means that this bundle could not be correctly installed from a default Symfony 2.3 project. The `post-package-install` composer settings links to some event listener which is not available in release 1.0.1.

All in all this bundle does nothing after a bundle requirement in a SF 2.3 project.