CodeStyle / Removed cannotBeOverwritten

- [x] better use statement order
- [x] cs fixing
- [x] removed white spaces
- [x] removed coupling with `\Symfony\Bridge\Monolog\Logger` , used `LoggerInterface` instead
- [x] removed `cannotBeOverwritten()` as it makes no sense since we should be able to override the api_key when we are in development to use the test api 

PS: You should activate the Ticket pannel on github and you should really **write some documentation** with some simple use example. I'd be the first happy.