Added the `Secure` annotation

This update allows you to do something like what is described at the
bottom of http://silex.sensiolabs.org/doc/providers/security.html
except with annotations.

I added a symfony/security suggest in composer.json to indicate that the
Symfony Security component is required to use this annotation
successfully.

I removed the composer.lock file because is is superfulous in a library
project.
Use the Security trait method if it exists
Merge pull request #1 from jdesrosiers/master

Added the `Secure` annotation