Require yaml explicitly. Needed for Ruby1.9. Features are not running…

… on 1.9 yet though.

Rakefile

@@ -53,6 +53,7 @@ task :default => :spec
 require 'rake/rdoctask'
 Rake::RDocTask.new do |rdoc|
   if File.exist?('VERSION.yml')
+    require 'yaml'
     config = YAML.load(File.read('VERSION.yml'))
     version = "#{config[:major]}.#{config[:minor]}.#{config[:patch]}"
   else