Add JSX+ES6 transformation test case

Author: eugenijusr

test/dummy/app/assets/javascripts/ecmascript6_example.es6.jsx

@@ -0,0 +1 @@
+<div/>;

test/react/jsx_test.rb

@@ -42,6 +42,13 @@ class JSXTransformTest < ActionDispatch::IntegrationTest
 
     assert_equal EXPECTED_JS.gsub(/\s/, ''), @response.body.gsub(/\s/, '')
   end
+  
+  test 'asset pipeline should transform JSX + ES6' do
+    get '/assets/ecmascript6_example.js'
+    assert_response :success
+    
+    assert_equal EXPECTED_JS.gsub(/\s/, ''), @response.body.gsub(/\s/, '')
+  end
 
   test 'asset pipeline should transform JSX + Coffeescript' do
     get '/assets/example2.js'