Suggestion: add a new method resetHostBase

[dimitrismitsis]

This is a suggestion after struggling to reset the host base, that needs resetting after the use of amOnUrl() http://codeception.com/docs/modules/WebDriver#amonurl

My suggestion is the following: Although, it can be written much better probably

    public function resetHostBase(){
        $config = \Codeception\Configuration::config();
        $url = $config["modules"]["config"]["WebDriver"]["url"];
        $this->amOnUrl($url);
    }

I believe that this function is needed in many cases after the use of amOnUrl() when using the WebDriver.

Thank you!