Removes dependency on active_support

[heythisisnate]

We were using cattr_accessor and class_inheritable_attribute which are part of active_support. I removed this dependency by just using regular ruby instead. The motivation for this is because class_inheritable_attribute has been removed from Rails 3.2, and there's no good reason to have a dependency on Rails anyway.

I also added a Gemfile, organized the gemspec a bit and removed a couple of other old dependencies that aren't necessary anymore.

Also, the default URL for MaxMind changed, so I updated that, too.

I have gem version 1.1.0 ready to go ... can you give me permission to push the gem? Just do

gem owner --add nate@nateclark.com