support integer ip addresses

I already store ip addresses in my database as integers. I would like to be able to do geocoding on these ip addresses without the intermediate step of first converting them to strings. This is good both for code simplicity and performance.

Separate issue: I ran `rake ensure_maxmind_files` prior to running specs. The database files I fetched contained the new country code you see in c47cd21c9965a25fe47a21fa5b27cd42385d5c17. I included the change in this PR so that the test suite would be 100% passing.