activesupport gem dependencies should reflect the versions we actually use

Gemfile

@@ -8,7 +8,6 @@ else
   gem 'arel'
 end
 
-gem 'minitest', '~> 3.2.0'
 gem 'mocha', '>= 0.11.2', :require => false
 gem 'rack-test', github: "brynary/rack-test"
 gem 'bcrypt-ruby', '~> 3.0.0'

activesupport/activesupport.gemspec

@@ -22,4 +22,5 @@ Gem::Specification.new do |s|
   s.add_dependency('i18n',       '~> 0.6')
   s.add_dependency('multi_json', '~> 1.3')
   s.add_dependency('tzinfo',     '~> 0.3.33')
+  s.add_dependency('minitest',   '~> 3.2')
 end

activesupport/lib/active_support/test_case.rb

@@ -1,3 +1,4 @@
+gem 'minitest' # make sure we get the gem, not stdlib
 require 'minitest/spec'
 require 'active_support/testing/setup_and_teardown'
 require 'active_support/testing/assertions'