integration refactoring

I think that the implementation of the TokenRepository, could implement and TokenVerifier interface, so this implementation could be skipped. 

```java
bind(TokenVerifier.class).to(PersistentTokenRepository.class);
bind(TokenRepository.class).to(PersistentTokenRepository.class); 
```

where in the test of PersistentTokenRepository, you could have: 
repository.registerToken(token); 
assertTrue(repository.verify(token));