Switch Rakefile over to Test::Unit.

Rakefile

@@ -5,7 +5,7 @@ Dir[File.expand_path(File.dirname(__FILE__)) + "/lib/tasks/**/*.rake"].sort.each
 
 RedminePluginSupport::Base.setup do |plugin|
   plugin.project_name = 'redmine_rate'
-  plugin.default_task = [:spec, :features]
+  plugin.default_task = [:test]
 end
 
 begin