integration refactoring

What do you mean harder for integration ? 

Here is the whole implementation of the generate() method.
```java
  @Override
  public Token generate() {
    String value = Hashing.sha1().hashBytes(UUID.randomUUID().toString().getBytes()).toString();
    String type = "bearer";

    return new Token(value, type);
  }
```

I think that we can remove the factory as whole and use this method as a private method, so the definition will be: 

```java
public void registerNewToken() {
   Token token = generate();
   datastore.get().store().instance(token).now();
}
```