fix typo "testGuy" -> "webGuy" in the chapter about pageObject actions

There was a confusion between 'webGuy' and 'testGuy' in the chapter about actions in pageObject.
Protected property $webGuy was declared but in method 'login' we had:
$I = $this->testGuy;
Merge pull request #460 from shofel/master

fix typo "testGuy" -> "webGuy" in the chapter about pageObject actions