Fix syntax error in example code

Close #80

README.md

@@ -181,7 +181,7 @@ same host as your test environment. In our example, we'll update both to
 
 ```ruby
 # tests/test_helper.rb
-ActionDispatch::IntegrationTest
+ActionDispatch::IntegrationTest do
   Capybara.server_port = 3001
   Capybara.app_host = 'http://localhost:3001'
 end