Ensure tests pass when running isolated

The array extension method `second` is used in some tests so ensure
that it is loaded so we can run test files individually.

Author: pixeltrix

test/test_helper.rb

@@ -1,5 +1,6 @@
 require "bundler/setup"
 require "active_support"
+require 'active_support/core_ext/array/access'
 require "rails/version"
 
 if Rails::VERSION::STRING > "4.0"