Add IPinfo Lite service

[iltempo]

IPinfo recently added a Lite service that allows unlimited free IP lookups on the country level. This PR adds support for that service.

The results do not contain location information. This is why some tests are skipped.

[abdullahdevrel]

Thank you very much! We really appreciate it.

We were hoping that someday people would help us bring our Lite DB to a geocoder, but we lack Ruby experts on our team. So, we genuinely appreciate you taking the time and writing the code to bring the Lite API to the project. Thanks!

— Abdullah | DevRel, IPinfo

[iltempo]

@abdullahdevrel, you are welcome. Considering the other open PRs, it may take some time for this to receive feedback or even get merged.

Is your request about LITE DB related to the "ancient" PR #1324?

[alexreisner]

This looks like a great service. And thank you for the clean, easy-to-review PR. Everything looks good except that the methods in lib/geocoder/results/ipinfo_io_lite.rb appear to be defined twice. You should either define them explicitly or loop through response_attributes and define them dynamically. Can you fix that and I'll merge?

[iltempo]

Thank you for the quick review and the feedback @alexreisner. I fixed the PR and added some general information about the service to a readme file, which I did not spot in the first place.

[alexreisner]

Excellent. This looks great. Thanks!

[abdullahdevrel]

@iltempo

Is your request about LITE DB related to the "ancient" PR #1324?

Oh no. That company is not us.

I was referring to this request: #1632

However, instead of the IP to Country ASN database, it should now be the IPinfo Lite Database. We have changed the schema for it.

https://ipinfo.io/developers/ipinfo-lite-database

The implementation would be similar to MaxMind's MMDB-based implementation because our data also comes in MMDB format.