Add function to check to just see if a cookie is present or not

[kenjis]

This PR enables you can write a test like the following:

	public function test_cookie_is_just_set()
	{
		$output = $this->request('GET', 'set_cookie/name_and_value');
		$this->assertResponseCookie(
			'The-Cookie-Name', $this->anything()
		);
	}

[coveralls]

Changes Unknown when pulling 5984e24 on add-to-check-cookie-is-present-or-not into ** on master**.