url: reslove urls with . and ..

'.' and '..' are directory specs and resolving urls with or without the
hostname with '.' and '..' should add a trailing slash to the end of the
url.

Fixes: https://github.com/joyent/node/issues/8992
PR-URL: https://github.com/joyent/node/pull/9010


Reviewed-by: Trevor Norris <trev.norris@gmail.com>