Fix acceptance tests where we should be using Bundler

spec/acceptance/active_model_integration_spec.rb

@@ -14,7 +14,7 @@ describe 'shoulda-matchers integrates with an ActiveModel project' do
       puts "Loaded all dependencies without errors"
     FILE
 
-    result = run_command('bundle exec ruby load_dependencies.rb')
+    result = run_command_within_bundle('ruby load_dependencies.rb')
     expect(result).to have_output('Loaded all dependencies without errors')
   end
 end

spec/support/acceptance/helpers/step_helpers.rb

@@ -67,7 +67,7 @@ module AcceptanceTests
     end
 
     def run_n_unit_tests(*paths)
-      run_command 'ruby -I lib -I test', *paths
+      run_command_within_bundle 'ruby -I lib -I test', *paths
     end
 
     def run_n_unit_test_suite