This was the last lingering dependency. I was able to convert almost every method to request and parse YAML instead of JSON but I got stuck on rubygems/gemcutter#323. Ruby 1.9 includes JSON as part of the standard library, so by requiring 1.9, I don't need to specify it as a dependency. Users of older Ruby versions can hack around this constraint by force-installing the gem and requiring a JSON library manually. Closes #4.