load this package with `require 'geoip-c'`

I have changed the package name from 'geoip' to 'geoip-c' as same as rubygem name.
This is why I thought to be renamed for this package.

* `require 'geoip'` is usual way.
http://rubygems.org/gems/geoip

* `require 'geoip'` is like tricky. It could not use together.
http://rubygems.org/gems/geoip-c