SF 5 compatibility

Fixed SF 5 compatibility without breaking SF < 4.2 versions.
Thanks @scar63 !

Backward compatibility bug fix

Fixed a critical bug on SF 3.4 (#22)

Symfony 4.2 compatibility

Fixed deprecation in TreeBuilder and a bug when authentication fails

Global logout and failure event

• New service to logout remotely from the CAS server when logging out from the app (see #13)
• New authentication failure event listener

Symfony 4 compatibility

Now compatible with Symfony 4
Thanks @cilefen for your work

Better URLs

URL management is much better, CAS tokens are no longer exposed to the user.
Thank you @adamfranco for this PR !

Use of Guzzle

The bundle is now more configurable and uses Guzzle library to send HTTP requests to the CAS server.
Thanks to webmastard !

First release

This is the first functional release.