Remove `ActionController::IntegrationTest`

* Replace `ActionController::IntegrationTest` with
  `ActionDispatch::IntegrationTest`

https://github.com/rails/rails/blob/9c195344a83c406f29738dc5ff78b322f48132c7/guides/source/4_1_release_notes.md#removals-1
Merge pull request #1 from notonthehighstreet/rails4

Remove `ActionController::IntegrationTest`