switch to json format, use yajl-ruby for faster parsing
Modernize gem

Hadn't touched this project for a long time. So many out of date habits on
display!

* Remove Jeweler
* Remove rdoc cruft
* Clean up Rakefile
* Move deps into gemspec
Move to MultiJson

Yajl was chosen back when I started this project as it was the fastest JSON
parser around. But the JSON situation in Ruby is a mess and MultiJson lets
people use whichever JSON gem their project already requires.
Clean up specs

Some daft old habits to be found in here too. Multiple assertions, "should"
everywhere...
Move JSON out of project

Massaged Maxmind data is available at the below path. Users must set the data
path before use.

`City.data_path = '/path/to/dir'`

https://s3-us-west-2.amazonaws.com/cities-gem/cities.tar.gz
Update readme

Info about downloading JSON data. Code syntax highlighting.