Implementing LoggerAwareInterface.

Thanks for writing this twitter client. I thought it would be useful to set a logger after creation, so implemented `Psr\Log\LoggerAwareInterface`.

Merry Christmas!
Only set logger is part of the interface. So Could you remove this method? Thanks. ([ref](https://github.com/php-fig/log/blob/master/Psr/Log/LoggerAwareInterface.php#L16)).

If it's for test, just use the reflection in test env.

Thanks ;)