Cookie was only deleted from current path

Before cookies were removed by setting their expiration to past date. This approach however had no effect, when cookie was set on different path, then the page where it's removal is attempted.

For example cookie set using `document.cookie = "some_cookie=ok; path=/";` was impossible to delete when user was on `/some/sub-page.html` and a code `document.cookie = "some_cookie=; expires=Thu, 01 Jan 1970 00:00:00 GMT";` was executed.

In this PR I'm also removing a cookie (the `->setCookie('cookie_name')` method) from all possible paths on this current domain.

Tests in https://github.com/Behat/Mink/pull/418