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/iojs/io.js/pull/278


Reviewed-By: Trevor Norris <trev.norris@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>