Config option to disable GeoIP database

[3meraldK]

No description provided.

[ljacqu]

I don't think the constructor is the correct place to check for this, but rather in isDataAvailable(). It's not just called by the constructor but also in lookup methods, so it would be better to properly catch it in isDataAvailable and to avoid conditional logic in the constructor.

[3meraldK]

Requesting @ljacqu to review

[ljacqu]

Two unit tests fail, and I think we don't need the enabled field since all public data methods go through getCountry() -> I will fix this

[ljacqu]

The changes are now on master. Thanks!