Update documentation

[piranna]

Since project is using MaxMind database, docs are wrong to say it's using a SQLite one. Update this an any other reference to how the project works and its API, specially how to set the database to use :-)

[piranna]

Ok, my wrong... it's actually using SQLite, the changelog confused me to think that it was being using directly the MaxMind database. Would it make sense? Currently it's being used a single table, so probably by using MaxMind optimized one would not be needed to do the conversion but also could be faster to fetch the info... what do you think?

[vangheem]

Sure, I'm open to PRs!