Merge pull request #614 from arthurnn/fix_build_40

Fix rails 4.0.x build.

.gitignore

@@ -16,3 +16,4 @@ test/tmp
 test/version_tmp
 tmp
 *.swp
+.ruby-version

.travis.yml

@@ -15,6 +15,4 @@ matrix:
   allow_failures:
     - rvm: ruby-head
     - env: "RAILS_VERSION=master"
-    - env: "RAILS_VERSION=4.0"
     - env: "RAILS_VERSION=3.2"
-

test/test_helper.rb

@@ -5,6 +5,8 @@ require 'action_controller'
 require 'action_controller/test_case'
 require "active_support/json"
 require 'minitest/autorun'
+# Ensure backward compatibility with Minitest 4
+Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)
 
 require "active_model_serializers"