[CI SKIP] Add note about compatibility with RSpec.

Author: tgxworld

README.md

@@ -23,6 +23,20 @@ Or install it yourself as:
 
     $ gem install rails-controller-testing
 
+### RSpec
+
+See https://github.com/rspec/rspec-rails/issues/1393.
+
+To work around the issue, you'll have to include the modules in your `spec_helper`.
+
+```ruby
+RSpec.configure do |config|
+  config.include Rails::Controller::Testing::TestProcess
+  config.include Rails::Controller::Testing::TemplateAssertions
+  config.include Rails::Controller::Testing::Integration
+end
+```
+
 ## Usage
 
 ### assigns