No need for a gem for this one.
Simple Migration and Seeds file for adding Languages to your Rails app.
Run the migration or use the rails generator
rails g model Language name:string:index iso_639_1:string:index iso_639_2t:string:index iso_639_2b:string iso_639_3:string:index scope:string type_of:string endonyms:string other_names:string notes:text
Copy over your seeds, seed them in your usual way, and viola!
Here is a gist with a rake task that will allow you to import these seeds from the file directly:
https://gist.github.com/CromonMS/2edc3ccc254ef9baa34d61252530a566
That's it!
If there are changes / updates to the country list, you can run the parser to update the seeds file.
ruby parse_wiki.rb
When you run the parser there are a few languages that may need manually fixing, mostly due to punctuation and quotations etc.
I do not have time to work out the problem, more than happy to take a pull request that deals with the errors that happen.