Move from Test::Unit to Minitest.

Gemfile

@@ -25,7 +25,7 @@ gem 'activesupport', '~> 3.2.13'
 gem 'jekyll_test_plugin'
 gem 'jekyll_test_plugin_malicious'
 gem 'liquid-c', '~> 0.0.3'
-gem 'minitest' if RUBY_PLATFORM =~ /cygwin/
+gem 'minitest'
 gem 'test-unit' if RUBY_PLATFORM =~ /cygwin/ || RUBY_VERSION.start_with?("2.2")
 
 if ENV['BENCHMARK']

test/helper.rb

@@ -6,8 +6,8 @@ SimpleCov.start('gem') do
 end
 
 require 'rubygems'
-require 'test/unit'
 require 'ostruct'
+require 'minitest/autorun'
 
 require 'jekyll'
 
@@ -23,9 +23,7 @@ include Jekyll
 # Send STDERR into the void to suppress program output messages
 STDERR.reopen(test(?e, '/dev/null') ? '/dev/null' : 'NUL:')
 
-class Test::Unit::TestCase
-  include RR::Adapters::TestUnit
-
+class Minitest::Test
   def fixture_site(overrides = {})
     Jekyll::Site.new(site_configuration(overrides))
   end