Migrate the integration tests to minitest, too

features/step_definitions/jekyll_steps.rb

@@ -27,7 +27,7 @@ After do
   Dir.chdir(File.dirname(TEST_DIR))
 end
 
-World(Test::Unit::Assertions)
+World(Minitest::Assertions)
 
 Given /^I have a blank site in "(.*)"$/ do |path|
   FileUtils.mkdir_p(path) unless File.exist?(path)
@@ -191,7 +191,7 @@ Then /^I should see exactly "(.*)" in "(.*)"$/ do |text, file|
 end
 
 Then /^I should not see "(.*)" in "(.*)"$/ do |text, file|
-  assert_no_match Regexp.new(text, Regexp::MULTILINE), file_contents(file)
+  refute_match Regexp.new(text, Regexp::MULTILINE), file_contents(file)
 end
 
 Then /^I should see escaped "(.*)" in "(.*)"$/ do |text, file|

features/support/env.rb

@@ -1,7 +1,7 @@
 require 'fileutils'
 require 'posix-spawn'
 require 'rr'
-require 'test/unit'
+require 'minitest/assertions'
 require 'time'
 
 JEKYLL_SOURCE_DIR = File.dirname(File.dirname(File.dirname(__FILE__)))