Fix #31: Error with symfony 3.1 and symfony 3.2.

[mekras]

See #31.

[Moinax]

Hi @mekras ,

First of all, thank you for your PR.

As you may see, the ImageTypeExtension is used to extend the suggested https://github.com/snowcap/SnowcapCoreBundle

In order to make this work correctly, there is a few things to do:

• First we need a PR on the SnowcapCoreBundle to update the FormTypes, the FormExtensions, the composer.json and the documentation
• Then we need to extend the SnowcapCoreBundle/Form/Type/ImageType instead of Symfony\Component\Form\Extension\Core\Type\FormType
• As the SnowcapCoreBundle is only suggested, we should remove the ImageTypeExtension from the services.yml and update the documentation to explain how to add it in our project services.yml
• Finally, we need to update the composer.json to update the requirements if it is not compatible with Symfony 2.7.

Thank you in advance for your help on this.

Regards,

[mekras]

OK, I'll try to help with this.

[ickbinhier]

@Moinax can you plaese merge this request.
and make please a new release.