Cookie was only deleted from current path

When deleting a cookie using `->setCookie('cookieName')` code, then only cookie from current path was deleted. This way if cookie was set on `/index.html` page, then it could not be deleted, while being on `/sub-folder/sub-page.html`.

Here I'm also bringing `->reset()` method of Session up to date with other drivers, so now it ONLY deletes all cookies and nothing more. Before it was also erasing browser history, which prevented `->reload()` method from working properly after session reset.

Tests in https://github.com/Behat/Mink/pull/418