fix: don't remove the prefix from the request path (#13)

The request path is used later when pushing related resources and push
doesn't work if a path is not absolute.

Also don't remove the query part of the url either because related
resources may be different depending on the query part.

Also importantly, this PR fixes the cookie path for the cache cookie. It
must be set to the root path (/). If `path` is not specified, it
defaults to the current request path, which is wrong.

Additional changes:
- revert to `require('../..')` in the sample app. `npm install` for file
  URLs is brittle and often fails with cryptic errors.
- update packages.