updated composer & travis usage, added twig function: feature_enabled, f...

hi, i made some modernisations and added a new function:
 
- added a twig functions: feature_enabled , so i can be used in if/else clause f.e. for literals
- updated composer requirements
- updated phpunit autoloader to use composer
- updated travis config to use composer

hope this can be merged and tagged.

btw:
Is this bundle on packagist? i couldnt find it.