added cookie/headers debug info

related to this issue: https://github.com/Codeception/Codeception/issues/774.
Works like this:
```yaml
* I expect to see validations errors
* I see "Incorrect username or password."
* I am going to try to login with correct credentials
* I submit form "#login-form",{"LoginForm[username]":"admin","LoginForm[password]":"admin"}
  [Uri] /web/index-test-functional.php?r=site/login
  [Method] post
  [Parameters] {"LoginForm":{"username":"admin","password":"admin","rememberMe":"0"}}
  [Response] 200
  [Page] http://localhost/home/mark/basic_db_cleaner/web/index-test-functional.php
  [Cookies] []
  [Headers] {"content-type":["text\/html; charset=UTF-8"]}
* I expect to see user info
* I see "Logout (admin)"
```