Fix deprecations for twig 3 (#28)

Added Symfony 6 compatibility

Added Symfony 4/5 compatibility

* Added service auto-wiring support for Symfony 4.0

Merge pull request #26 from opensky/feature/RuntimeProvider-has-to-lo…

…ok-at-container

Check container as well as the initalized parameter array.

Merge pull request #24 from nopolabs/patch-2

fix isset optimization

Merge branch 'master' into 2.0

updated minimum symfony requirement to 2.3

replaced deprecated twig function

removed branch alias

removed minimum-stability: dev from composer.json