drop Symfony 2.2 support

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | yes (bumped dependency)
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Not sure if we should bump these requirements or only for Bundles that dependent on the FrameworkBundle