Use bundler to manage our four dependencies.

.gitignore

@@ -1,3 +1,4 @@
+Gemfile.lock
 doc
 pkg
 tmp/*

Gemfile

@@ -0,0 +1,12 @@
+source 'https://rubygems.org'
+
+gemspec
+
+group :test do
+  gem 'addressable'
+end
+
+group :development do
+  gem 'rake'
+  gem 'kramdown'
+end

Rakefile

@@ -1,36 +1,18 @@
-require 'rubygems'
-require 'rake'
-
 begin
-  gem 'rubygems-tasks', '~> 0.1'
-  require 'rubygems/tasks'
-
-  Gem::Tasks.new
+  require 'bundler/setup'
 rescue LoadError => e
-  warn e.message
-  warn "Run `gem install rubygems-tasks` to install 'rubygems/tasks'."
+  abort e.message
 end
 
-begin
-  gem 'rspec', '~> 3.0'
-  require 'rspec/core/rake_task'
+require 'rake'
 
-  RSpec::Core::RakeTask.new
-rescue LoadError => e
-  task :spec do
-    abort "Please run `gem install rspec` to install RSpec."
-  end
-end
+require 'rubygems/tasks'
+Gem::Tasks.new
+
+require 'rspec/core/rake_task'
+RSpec::Core::RakeTask.new
 task :test => :spec
 task :default => :spec
 
-begin
-  gem 'yard', '~> 0.6'
-  require 'yard'
-
-  YARD::Rake::YardocTask.new  
-rescue LoadError => e
-  task :yard do
-    abort "Please run `gem install yard` to install YARD."
-  end
-end
+require 'yard'
+YARD::Rake::YardocTask.new