Change Ipinfodb to be a module

If we don't instantiate it, there's no need for it to be a class.
https Rubygems source
Extract VERSION constant into a separate file

Following standard Ruby gems convention.
Add tmp/ to .gitignore
Remove Gemfile.lock from the repo
Move main library into lib/ipinfodb/lookup.rb
Add 'rake' as development dependency
Don't need to require rubygems
Rename 'test.rb' to 'test_helper.rb'
Rakefile cleanup

Make it more modern/conventional.
Make 'test' the default Rake task
Add integration test for actual geolocation

i.e. use some real IP address.
Update to IPInfoDB API v3
Add exemplary API response to README
Convert README to Markdown
Add Copyright notes and LICENSE file
Add myself to authors in gemspec