Admin UI relationships do not referring correctly (urls are incorrect)

[kossel]

Inside the admin UI, relationships does not mapping url correctly.
Eg. in post table, user column element are mapping to
undefined/users/:id
instead of
/users/:id

Steps to reproduce:
git clone the repo
npm install
create a new post

if you click on the element, will cause #27 issue

npm 3.5.0
keystone-demo 95fe3e6