Update generating_urls.md
Add updatedAt attribute
Fix uppercase u in Null.
Improved documentation

In older Symfony versions you have to define {{ form_enctype(upload_form) }}
Add a few functional tests
Remove useless steps in the travis-ci configuration
Remove useless dependencies for functional tests
Fix test dependencies
Switch to PSR-4
Update minimum Symfony version to 2.3
Simplify travis configuration
Directly specify the version constraint on symfony/symfony
Update UPGRADE guide for v0.11.0
Override the default text 'File' in the label 

On the all form rendered, the label are the same text 'File', get the parent attribute
Fix a few broken links in the doc
Disable xdebug for travis-ci builds
resolveUri return null if filename empty for file system storage