Fixed the generated test in the redmine_plugin_model. (#3927)

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@2926 e93f8b46-1217-0410-a6f0-8f06a7374b81

lib/generators/redmine_plugin_model/templates/unit_test.rb.erb

 require File.dirname(__FILE__) + '/../test_helper'
 
-class <%= class_name %>Test < Test::Unit::TestCase
+class <%= class_name %>Test < ActiveSupport::TestCase
   fixtures :<%= table_name %>
 
   # Replace this with your real tests.