Addressable is a replacement for the URI implementation that is part of Ruby's standard library. It more closely conforms to the relevant RFCs and adds support for IRIs and URI templates.
You know what to do:
sudo gem install addressable
Alternatively, you can:
git submodule add
git://github.com/sporkmonger/addressable.git
vendor/gems/addressable
Addressable works in Ruby 1.8.x, 1.9.x, and JRuby.