RFC6265 compliant cookie default path and path mathing

I encountered a problem where server sets a cookie without path specified. The request path would be used. However if request path is something like `/file.php`, then cookie will have exactly same path and won't match any other requests. 
I implemented RFC6265 cookie path selection and path matching.

Please note that _cookie_ path `/path/` would not match _request_ path `/path` (no trailing slash). This is described in RFC section 5.1.4, Firefox behaves the same way.